CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of currently pending U.S. application Ser. No. 11/068,719, filed Feb. 28, 2005, entitled TRANSMISSION CONTROL PROTOCOL/INTERNET PROTOCOL (TCP/IP) PACKET-CENTRIC WIRELESS POINT TO MULTI-POINT (PtMP) TRANSMISSION SYSTEM ARCHITECTURE, which is a continuation of U.S. application Ser. No. 09/349,477, filed Jul. 9, 1999, entitled TRANSMISSION CONTROL PROTOCOL/INTERNET PROTOCOL (TCP/IP) PACKET-CENTRIC WIRELESS POINT TO MULTI-POINT (PtMP) TRANSMISSION SYSTEM ARCHITECTURE, which issued as U.S. Pat. No. 6,862,622, on Mar. 1, 2005, and which claims the benefit of priority from U.S. Provisional Patent Application No. 60/092,452, filed Jul. 10, 1998, the disclosures of each are incorporated herein by reference thereto.

The following applications of common assignee contain common disclosure:

- U.S. patent application entitled â€œQuality of Service (QoS)â€”Aware Wireless Point to Multi-Point (PtMP) Transmission System Architecture,â€ filed Jul. 9, 1999, assigned U.S. application Ser. No. 09/349,480, now abandoned.
- U.S. patent application entitled â€œMethod for Providing Dynamic Bandwidth Allocation Based on IP-Flow Characteristics in a Wireless Point to Multi-Point (PtMP) Transmission System,â€ filed Jul. 9, 1999, assigned U.S. application Ser. No. 09/350,126, now abandoned.
- U.S. patent application entitled â€œMethod for Providing for Quality of Service (QoS)â€”Based Handling of IP-Flows in a Wireless Point to Multi-Point Transmission System,â€ filed Jul. 9, 1999, assigned U.S. application Ser. No. 09/350,118, now abandoned.
- U.S. patent application entitled â€œIP-Flow Identification in a Wireless Point to Multi-Point Transmission System,â€ filed Jul. 9, 1999, assigned U.S. application Ser. No. 09/347,856, issued as U.S. Pat. No. 6,594,246.
- U.S. patent application entitled â€œIP-Flow Characterization in a Wireless Point to Multi-Point (PtMP) Transmission System,â€ filed Jul. 9, 1999, assigned U.S. application Ser. No. 09/350,150, issued as U.S. Pat. No. 6,590,885.
- U.S. patent application entitled â€œIP-Flow Classification in a Wireless Point to Multi-Point (PtMP) Transmission System,â€ filed Jul. 9, 1999, assigned U.S. application Ser. No. 09/350,156, issued as U.S. Pat. No. 6,452,915.
- U.S. patent application entitled â€œIP-Flow Prioritization in a Wireless Point to Multi-Point (PtMP) Transmission System,â€ filed Jul. 9, 1999, assigned U.S. application Ser. No. 09/349,476, now abandoned.
- U.S. patent application entitled â€œMethod of Operation for Providing for Service Level Agreement (SLA) Based Prioritization in a Wireless Point to Multi-Point (PtMP) Transmission System,â€ filed Jul. 9, 1999, assigned U.S. application Ser. No. 09/350,170, now abandoned.
- U.S. patent application entitled â€œMethod for Transmission Control Protocol (TCP) Rate Control With Link-Layer Acknowledgments in a Wireless Point to Multi-Point (PtMP) Transmission System,â€ filed Jul. 9, 1999, assigned U.S. application Ser. No. 09/349,481, now abandoned.
- U.S. patent application entitled â€œTransmission Control Protocol/Internet Protocol (TCP/IP)â€”Centric QoS Aware Media Access Control (MAC) Layer in a Wireless Point to Multi-Point (PtMP) Transmission System,â€ filed Jul. 9, 1999, assigned U.S. application Ser. No. 350,159, now abandoned.
- U.S. patent application entitled â€œUse of Priority-Based Scheduling for the Optimization of Latency and Jitter Sensitive IP Flows in a Wireless Point to Multi-Point Transmission System,â€ filed Jul. 9, 1999, assigned U.S. application Ser. No. 09/347,857, now abandoned.
- U.S. patent application entitled â€œTime Division Multiple Access/Time Division Duplex (TDMA/TDD) Access Method for a Wireless Point to Multi-Point Transmission System,â€ filed Jul. 9, 1999, assigned U.S. application Ser. No. 09/349,475, now abandoned.
- U.S. patent application entitled â€œReservation Based Prioritization Method for Wireless Transmission of Latency and Jitter Sensitive IP-Flows in a Wireless Point to Multi-Point Transmission System,â€ filed Jul. 9, 1999, assigned U.S. application Ser. No. 09/349,483, issued as U.S. Pat. No. 6,628,629.
- U.S. patent application entitled â€œTranslation of Internet-Prioritized Internet Protocol (IP)-Flows into Wireless System Resource Allocations in a Wireless Point to Multi-Point (PtMP) Transmission System,â€ filed Jul. 9, 1999, assigned U.S. application Ser. No. 09/349,479, now abandoned.
- U.S. patent application entitled â€œMethod of Operation for the Integration of Differentiated services (Diff-serv) Marked IP-Flows into a Quality of Service (QoS) Priorities in a Wireless Point to Multi-Point (PtMP) Transmission System,â€ filed Jul. 9, 1999, assigned U.S. application Ser. No. 09/350,162, now abandoned.
- U.S. patent application entitled â€œMethod for the Recognition and Operation of Virtual Private Networks (VPNs) over a Wireless Point to Multi-Point (PtMP) Transmission System,â€ filed Jul. 9, 1999, assigned U.S. application Ser. No. 09/349,975, issued as U.S. Pat. No. 6,680,922.
- U.S. patent application entitled â€œTime Division Multiple Access/Time Division Duplex (TDMA/TDD) Transmission Media Access Control (MAC) Air Frame,â€ filed Jul. 9, 1999, assigned U.S. application Ser. No. 09/350,173, now abandoned.
- U.S. patent application entitled â€œApplicationâ€”Aware, Quality of Service (QoS) Sensitive, Media Access Control (MAC) Layer,â€ filed Jul. 9, 1999, assigned U.S. application Ser. No. 09/349,482, issued as U.S. Pat. No. 6,640,248.
- U.S. patent application entitled â€œTransmission Control Protocol/Internet Protocol (TCP/IP) Packet-Centric Wireless Point to Point (PtP) Transmission System Architecture,â€ filed Jul. 9, 1999, assigned U.S. application Ser. No. 09/349,478, now abandoned.
- U.S. patent application entitled â€œTransmission Control Protocol/Internet Protocol (TCP/IP) Packet-Centric Cable Point to Multi-Point (PtMP) Transmission System Architecture,â€ filed Jul. 9, 1999, assigned U.S. application Ser. No. 09/349,474, now abandoned.
- U.S. patent application entitled â€œMethod and Computer Program Product for Internet Protocol (IP)-Flow Classification in a Wireless Point to Multi-Point (PtMP) Transmission System,â€ filed Oct. 24, 2002, assigned U.S. application Ser. No. 10/241,454.
- U.S. patent application entitled â€œUse of Priority-Based Scheduling for the Optimization of Latency and Jitter Sensitive IP Flows in a Wireless Point to Multi-Point Transmission System,â€ filed Aug. 10, 2006, assigned U.S. application Ser. No. 11/502,583.
- U.S. patent application entitled â€œQuality of Service (QoS)â€”Aware Wireless Point to Multi-Point (PtMP) Transmission System Architecture,â€ filed Aug. 10, 2006, assigned U.S. application Ser. No. 11/502,596.
- U.S. patent application entitled â€œMethod for Providing for Quality of Service (QoS)â€”Based Handling of IP-Flows in a Wireless Point to Multi-Point Transmission System,â€ filed Aug. 10, 2006, assigned U.S. application Ser. No. 11/502,348.
- U.S. patent application entitled â€œTransmission Control Protocol/Internet Protocol (TCP/IP)â€”Centric QoS Aware Media Access Control (MAC) Layer in a Wireless Point to Multi-Point (PtMP) Transmission System,â€ filed Aug. 10, 2006, assigned U.S. application Ser. No. 11/502,599.
- U.S. patent application entitled â€œMethod of Operation for the Integration of Differentiated Services (DiffServ) Marked IP-Flows into a Quality of Service (QoS) Priorities in a Wireless Point to Multi-Point (PtMP) Transmission System,â€ filed Aug. 10, 2006, assigned U.S. application Ser. No. 11/502,101.
- U.S. patent application entitled â€œTime Division Multiple Access/Time Division Duplex (TDMA/TDD) Transmission Media Access Control (MAC) Air Frame,â€ Aug. 10, 2006, assigned U.S. application Ser. No. 11/502,601.

FIELD OF THE INVENTION

The present invention relates generally to telecommunications and, more particularly, to a system and method for implementing a QoS aware wireless point-to-multi-point transmission system.

BACKGROUND OF THE INVENTION

Telecommunication networks such as voice, data and video networks have conventionally been customized for the type of traffic each is to transport. For example, voice traffic is very latency sensitive but quality is less important, so voice networks are designed to transport voice traffic with limited latency. Traditional data traffic, such as, e.g., a spreadsheet, on the other hand is not latency sensitive, but error-free delivery is required. Conventional telecommunications networks use circuit switching to achieve acceptable end user quality of service (QoS). With the advent of new packet switching high bandwidth data networks, different types of traffic can be transported over a data network. Specifically, convergence of separate voice, data and video networks into a single broadband telecommunications network is enabled. To ensure end user satisfaction, a system is desired that provides QoS for various types of traffic to be transported.

Wireless networks present particular challenges over their wireline counterparts in delivering QoS. For example, wireless networks traditionally exhibit high bit error rates (BER) due to a number of reasons. Conventional wireless networks also implement circuit switched connections to provide reliable communications channels. However the use of circuit switched connections allocates bandwidth between communicating nodes whether or not traffic is constantly being transferred between the nodes. Therefore, circuit switched connections use communications bandwidth rather inefficiently.

Packet switching makes more efficient use of available bandwidth than does traditional circuit switching. Packet switching breaks up traffic into so-called â€œpacketsâ€ which can then be transported from a source node to a destination for reassembly. Thus a particular portion of bandwidth can be shared by many sources and destinations yielding more efficient use of bandwidth.

A wireless broadband access telecommunications system is desired which can provide a QoS capability that is comparable to that delivered by wireline broadband access devices. Conventionally, one of the barriers to the deployment of wireless broadband access systems has been the absence of acceptable QoS characteristics, while at the same time delivering bandwidth sufficient to qualify as broadband. Delivery of raw bandwidth over wireless media without acceptable QoS would not benefit end users. Likewise, the delivery of a high level of QoS at the cost of sufficient bandwidth would also not benefit end users.

Conventional efforts to provide wireless broadband access systems have not granted sufficient priority to QoS as a guiding principle in architecting the wireless systems, resulting in sub-optimal designs. With the rapid emergence of the Internet, the packet switching paradigm, and transmission control protocol/internet protocol (TCP/IP) as a universal data protocol, it has become clear that a new wireless system design has become necessary.

What is needed then is an IP-centric wireless broadband access system with true QoS capabilities.

SUMMARY OF THE INVENTION

The present invention is directed to a packet-centric wireless point to multi-point telecommunications system including: a wireless base station communicating via a packet-centric protocol to a first data network; one or more host workstations communicating via the packet-centric protocol to the first data network; one or more subscriber customer premise equipment (CPE) stations coupled with the wireless base station over a shared bandwidth via the packet-centric protocol over a wireless medium; and one or more subscriber workstations coupled via the packet-centric protocol to each of the subscriber CPE stations over a second network. The packet-centric protocol can be transmission control protocol/internet protocol (TCP/IP). The packet-centric protocol can be a user datagram protocol/internet protocol (UDP/IP).

The system can include a resource allocation means for allocating shared bandwidth among the subscriber CPE stations. The resource allocation is performed to optimize end-user quality of service (QoS). The wireless communication medium can include at least one of: a radio frequency (RF) communications medium; a cable communications medium; and a satellite communications medium. The wireless communication medium can further include a telecommunications access method including at least one of: a time division multiple access (TDMA) access method; a time division multiple access/time division duplex (TDMA/TDD) access method; a code division multiple access (CDMA) access method; and a frequency division multiple access (FDMA) access method.

The first data network includes at least one of: a wireline network; a wireless network; a local area network (LAN); and a wide area network (WAN). The second network includes at least one of: a wireline network; a wireless network; a local area network (LAN); and a wide area network (WAN).

The system of claim 1 can include a resource allocator that allocates shared bandwidth among the subscriber CPE stations. The resource allocator optimizes end-user quality of service (QoS). The resource allocator can be application aware as well.

The cross-referenced applications listed above are incorporated herein by reference in their entireties.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described with reference to the accompanying figures, wherein:

FIG. 1A

is a block diagram providing an overview of a standard telecommunications network providing local exchange carrier services within one or more local access and transport areas;

FIG. 1B

depicts an exemplary network including workstations coupled to a data network;

FIG. 1C

illustrates a conventional video network, such as for example a cable television (CATV) network;

FIG. 2A

is a block diagram illustrating an overview of a standard telecommunications network providing both local exchange carrier and interexchange carrier services between subscribers located in different local access and transport areas;

FIG. 2B

illustrates a signaling network in detail;

FIG. 2C

illustrates an exemplary network carrying voice, data and video traffic over a data network;

FIG. 2D

depicts a network including a point-to-multipoint wireless network coupled via a router to a data network;

FIG. 3A

depicts an exemplary perspective diagram of a point-to-multipoint network;

FIG. 3B

depicts a block diagram further illustrating a wireless point-to-multipoint network;

FIG. 4

depicts a wireless Internet protocol network access architecture of the present invention;

FIG. 5A

depicts Internet protocol flows from a subscriber host to a wireless base station, and through a wireline connection to a destination host;

FIG. 5B

illustrates a functional flow diagram including an example functional description of a transmission control protocol adjunct agent performing an outgoing transmission control protocol spoof function;

FIG. 5C

illustrates a functional flow diagram including an exemplary functional description of a transmission control protocol adjunct agent performing an incoming transmission control protocol spoof function;

FIG. 6

illustrates a block diagram representing scheduling of mixed Internet protocol flows;

FIG. 7

illustrates packet header field information which can be used to identify Internet protocol flows and the quality of service requirements of the Internet protocol flows;

FIG. 8A

is a block diagram summarizing an exemplary downlink analysis, prioritization and scheduling function;

FIG. 8B

is a block diagram summarizing an exemplary uplink analysis prioritization and scheduling function;

FIG. 9

illustrates how a downlink flow scheduler can take into account a service level agreement in prioritizing a frame slot and scheduling resource allocation;

FIG. 10

depicts an embodiment of an inventive media access control hardware architecture;

FIG. 11

is an exemplary software organization for a packet-centric wireless point to multipoint telecommunications system;

FIG. 12A

illustrates an exemplary time division multiple access media access control air frame;

FIG. 12B

illustrates an exemplary structure for a time division multiple access/time division duplex air frame;

FIG. 12C

illustrates an exemplary downstream transmission subframe;

FIG. 12D

illustrates an exemplary upstream acknowledgment block field of a downstream transmission subframe;

FIG. 12E

illustrates an exemplary acknowledgment request block field of a downstream transmission subframe;

FIG. 12F

illustrates an exemplary frame descriptor block field of a downstream transmission subframe;

FIG. 12G

illustrates an exemplary downstream media access control payload data unit of a downstream transmission subframe;

FIG. 12H

illustrates an exemplary command and control block of a downstream transmission subframe;

FIG. 12I

illustrates an exemplary upstream transmission subframe;

FIG. 12J

illustrates an exemplary downstream acknowledgment block of an upstream transmission subframe;

FIG. 12K

illustrates an exemplary reservation request block of an upstream transmission subframe 1204;

FIG. 12L

illustrates an exemplary media access control payload data unit of an upstream transmission subframe;

FIGS. 12M

, 12N and 12O illustrate an exemplary operations data block of an upstream transmission subframe;

FIG. 13

illustrates how an exemplary flow scheduler for the present invention functions;

FIG. 14

is an exemplary two-dimensional block diagram of an advanced reservation algorithm;

FIG. 15A

is an exemplary logical flow diagram for a downlink flow analyzer;

FIG. 15B

is an exemplary logical flow diagram for a downlink flow scheduler;

FIG. 16A

is an exemplary logical flow diagram for an uplink flow analyzer;

FIG. 16B

is an exemplary logical flow diagram for an uplink flow scheduler;

FIG. 17

illustrates Internet protocol flow in a downlink direction, including Internet protocol security encryption; and

FIG. 18

illustrates an uplink direction of Internet protocol security support.

In the figures, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The figure in which an element first appears is indicated by the leftmost digit(s) in the reference number.

DETAILED DESCRIPTION OF THE INVENTION

I. An Example Environment

The present invention is described in terms of an example environment. The example environment uses a fixed wireless point-to-multi-point (PtMP) connection to transmit packetized data information including for example, IP telephony, video, data, received from a telecommunications carrier. As used herein, a telecommunications carrier can include US domestic entities (see Definitions below at section II) such as, e.g., ILECs, CLECs, IXCs, NGTs and Enhanced Service Providers (ESPs), as well as global entities such as PTTs and NEs, recognized by those skilled in the art. In addition, as used herein a telecommunications system includes domestic systems used by entities such as, e.g., ILECs, CLECs, IXCs and Enhanced Service Providers (ESPs), as well as global systems recognized by those skilled in the art.

In the preferred embodiment, the traffic arrives from a wide area network (WAN) connection.

Data traffic is received from a data network through a network router and can be demodulated from internet protocol (IP) format to, for example, the point-to-point protocol (PPP). Network routers can include, for example, a general purpose computer, such as the SUN workstation running routing software or a dedicated routing device such as various models from CISCO of San Jose, Calif., ASCEND of Alameda, Calif., NaETOPIA of Alameda, Calif., or 3COM of Santa Clara, Calif.

In the alternative, a virtual private networking protocol, such as the point-to-point tunneling protocol (PPTP), can be used to create a â€œtunnelâ€ between a remote user and a corporate data network. A tunnel permits a network administrator to extend a virtual private network from a server (e.g., a Windows NT server) to a data network (e.g., the Internet).

Although the invention is described in terms of this example environment, it is important to note that description in these terms is provided for purposes of illustration only. It is not intended that the invention be limited to this example environment or to the precise inter-operations between the above-noted devices. In fact, after reading the following description, it will become apparent to a person skilled in the relevant art how to implement the invention in alternative environments.

II. Definitions

Table 1 below defines common telecommunications terminology. These terms are used throughout the remainder of the description of the invention.

TABLE 1TermDefinitionaccess tandem (AT)An AT is a class 3/4 switch used to switch calls between EOs in aLATA. An AT provides subscribers access to the IXCs, to provide longdistance calling services. An access tandem is a network node. Othernetwork nodes can include, for example, a CLEC, or other enhancedservices provider (ESP), an international gateway or global point-of-presence (GPOP), or an intelligent peripheral (IP).bearer (B) channelsBearer (B) channels are digital channels used to carry both digital voiceand digital data information. An ISDN bearer channel is 64,000 bits persecond, which can carry PCM-digitized voice or data.called partyThe called party is the caller receiving a call sent over a network at thedestination or termination end.calling partyThe calling party is the caller placing a call over any kind of networkfrom the origination end.central office (CO)A CO is a facility that houses an EO homed. EOs are often called COs.class 1 switchA class 1 switching office, the Regional Center(RC), is the highest levelof local and long distance switching, or â€œoffice of last resortâ€ tocomplete a call.class 3 switchA class 3 switching office was a Primary Center (PC); an access tandem(AT) has class 3 functionality.class 4 switchA class 4 switching office was a Toll Center (TC) if operators werepresent or else a Toll Point (TP); an access tandem (AT) has class 4functionality.class 5 switchA class 5 switching office is an end office (EO) or the lowest level oflocal and long distance switching, a local central office. The switchclosest to the end subscriber.competitive LECCLECs are telecommunications services providers of local services that(CLEC)can compete with ILECs. Interprise and Century 21 are examples. ACLEC may or may not handle IXC services as well.competitive accessTeligent and Winstar are examples.providers (CAPS)customer premisesCPE refers to devices residing on the premises of a customer and used toequipment (CPE)connect to a telephone network, including ordinary telephones, keytelephone systems, PBXs, video conferencing devices and modems.digitized data (orDigitized data refers to analog data that has been sampled into a binarydigital data)representation (i.e., comprising sequences of 0's and 1's). Digitized datais less susceptible to noise and attenuation distortions because it is moreeasily regenerated to reconstruct the original signal.egress end officeThe egress EO is the node or destination EO with a direct connection tothe called party, the termination point. The called party is â€œhomedâ€ tothe egress EO.EgressEgress refers to the connection from a called party or termination at thedestination end of a network, to the serving wire center (SWC).end office (EO)An EO is a class 5 switch used to switch local calls within a LATA.Subscribers of the LEC are connected (â€œhomedâ€ ) to EOs, meaning thatEOs are the last switches to which the subscribers are connected.Enhanced ServiceA network services provider.Provider (ESP)equal access1+ dialing as used in U.S. domestic calling for access to any long distancecarrier as required under the terms of the modified final judgment (MFJ)requiring divestiture of the Regional Bell Operating Companies(RBOCs) from their parent company, AT&T.global point ofA GPOP refers to the location where international telecommunicationspresence (GPOP)facilities and domestic facilities interface, an international gateway POP.incumbent LECILECs are traditional LECs in the U.S., which are the Regional Bell(ILEC)Operating Companies (RBOCs). Bell South and U.S. West are examples.ILEC can also stand for an independent LEC such as a GTE.ingress end officeThe ingress EO is the node or serving wire center (SVC) with a directconnection to the calling party, the origination point. The calling partyis â€œhomedâ€ to the ingress EO.IngressIngress refers to the connection from a calling party or origination.integrated serviceAn ISDN Basic Rate Interface (BRI) line provides 2 bearer B channelsdigital network (ISDN)and 1 data D line (known as â€œ2B + Dâ€ over one or two pairs) to abasic rate interfacesubscriber.(BRI) lineintegrated servicesISDN is a network that provides a standard for communications (voice,digital network (ISDN)data and signaling), end-to-end digital transmission circuits, out-of-bandsignaling, and a features significant amount of bandwidth.inter machine trunkAn inter-machine trunk (IMT) is a circuit between two commonly-(IMT)connected switches.inter-exchange carrierIXCs are U.S. domestic long distance telecommunications services(IXC)providers. AT&T, MCI, Sprint, are examples.internet protocol (IP)IP is part of the TCP/IP protocols. It is used to recognize incomingmessages, route outgoing messages, and keep track of Internet nodeaddresses (using a number to specify a TCP/IP host on the Internet). IPcorresponds to the network layer of OSI.Internet serviceAn ISP is a company that provides Internet access to subscribers.provider (ISP)ISDN primary rateAn ISDN Primary Rate Interface (PRI) line provides the ISDNinterface (PRI)equivalent of a Tl circuit. The PRI delivered to a customer's premisescan provide 23B + D (in North America) or 30B + D (in Europe) channelsrunning at 1.544 megabits per second and 2.048 megabits per second,respectively.local exchange carrierLECs are local telecommunications services providers. Bell Atlantic and(LEC)U.S. West are examples.local access andA LATA is a region in which a LEC offers services. There are over 160transport area (LATA)LATAs of these local geographical areas within the United States.local area networkA LAN is a communications network providing connections between(LAN)computers and peripheral devices (e.g., printers and modems) over arelatively short distance (e.g., within a building) under standardizedcontrol.modified finalModified final judgment (MFJ) was the decision requiring divestiture ofjudgment (MFJ)the Regional Bell Operating Companies (RBOCs) from their parentcompany, AT&T.network nodeA network node is a generic term for the resources in atelecommunications network, including switches, DACS, regenerators,etc. Network nodes essentially include all non-circuit (transport)devices. Other network nodes can include, for example, equipment of aCLEC, or other enhanced service provider (ESP), a point-of-presence(POP), an international gateway or global point-of-presence (GPOP).new entrant (NE)A new generation global telecommunications.next generationA new telecommunications services provider, especially IP telephonytelephone (NGT)providers. Examples are Level 3 and Qwest.packetized voice orOne example of packetized voice is voice over internet protocol (VOIP).voice over a backboneVoice over packet refers to the carrying of telephony or voice traffic overa data network, e.g. voice over frame, voice over ATM, voice overInternet Protocol (IP), over virtual private networks (VPNs), voice over abackbone, etc.Pipe or dedicatedA pipe or dedicated communications facility connects an ISP to thecommunicationsinternet.facilitypoint of presenceA POP refers to the location within a LATA where the IXC and LEC(POP)facilities interface.point-to-pointA virtual private networking protocol, point-to-point tunneling protocoltunneling protocol(PPTP), can be used to create a â€œtunnelâ€ between a remote user and a(PPTP)data network. A tunnel permits a network administrator to extend avirtual private network (VPN) from a server (e.g., a Windows NTserver) to a data network (e.g., the Internet).point-to-point (PPP)PPP is a protocol permitting a computer to establish a connection withprotocolthe Internet using a modem. PPP supports high-quality graphical frontends, like Netscape.postal telephoneState regulated telephone companies, many of which are beingtelegraph (PTT)deregulated. NTT is an example.private branchA PBX is a private switch located on the premises of a user. The user isexchange (PBX)typically a private company which desires to provide switching locally.private line with a dialA private line is a direct channel specifically dedicated to a customer'stoneuse between two specified points. A private line with a dial tone canconnect a PBX or an ISP's access concentrator to an end office (e.g. achannelized Tl or PRI). A private line can also be known as a leasedline.public switchedThe PSTN is the worldwide switched voice network.telephone network(PSTN)regional Bell operatingRBOCs are the Bell operating companies providing LEC services aftercompanies (RBOCs)being divested from AT&T.signaling system 7SS7 is a type of common channel interoffice signaling (CCIS) used(SS7)widely throughout the world. The SS7 network provides the signalingfunctions of indicating the arrival of calls, transmitting routing anddestination signals, and monitoring line and circuit status.switching hierarchy orAn office class is a functional ranking of a telephone central officeoffice classificationswitch depending on transmission requirements and hierarchicalrelationship to other switching centers. Prior to AT&T's divestiture ofthe RBOCs, an office classification was the number assigned to officesaccording to their hierarchical function in the U.S. public switchednetwork (PSTN). The following class numbers are used: class 1 =Regional Center (RC), class 2 = Sectional Center (SC), class 3 =Primary Center (PC), class 4 = Toll Center (TC) if operators are presentor else Toll Point (TP), class 5 = End Office (EO) a local central office.Any one center handles traffic from one to two or more centers lower inthe hierarchy. Since divestiture and with more intelligent software inswitching offices, these designations have become less firm. The class 5switch was the closest to the end subscriber. Technology has distributedtechnology closer to the end user, diffusing traditional definitions ofnetwork switching hierarchies and the class of switches.telecommunicationsA LEC, a CLEC, an IXC, an Enhanced Service Provider (ESP), ancarrierintelligent peripheral (IP), an international/global point-of-presence(GPOP), i.e., any provider of telecommunications services.transmission controlTCP is an end-to-end protocol that operates at the transport and sessionsprotocol (TCP)layers of OSI, providing delivery of data bytes between processesrunning in host computers via separation and sequencing of IP packets.transmission controlTCP/IP is a protocol that provides communications betweenprotocol/internetinterconnected networks. The TCP/IP protocol is widely used on theprotocol (TCP/IP)Internet, which is a network comprising several large networksconnected by high-speed connections.TrunkA trunk connects an access tandem (AT) to an end office (EO).wide area networkA WAN is a data network that extends a LAN over the circuits of a(WAN)telecommunications carrier. The carrier is typically a common carrier.A bridging switch or a router is used to connect the LAN to the WAN.

III. Introduction

A. Quality of Service (QOS) in a Wireless Environment

The concept of quality of service (QoS) is one of the most difficult and least understood topics in data networking. Although a common term in data networking, there are many different usages and definitions for QoS, leading to confusion regarding an exact meaning in precise or quantitative terms. Even further confusion is found when attempts are made to measure or specify numeric quantities sufficient to allow comparison of equipment or network performance with respect to QoS.

The confusion about QoS in general data networking is transferred and magnified when applied to wireless data communications. Wireless transmission has a higher inherent bit error rate (BER) than does wireline transmission. The addition of, e.g., a point-to-multipoint (PtMP) topology for multiple users sharing a wireless medium makes it desirable that QoS be defined in a manner that specifically addresses the multiple complicating factors in wireless data communications.

To provide a non-ambiguous definition of QoS that applies to wireless data communications, the nature of the problem that QoS is meant to solve is helpful. Many of the problems of data communications over wireless are unique and distinct from those of wireline data communications, while some are in fact shared. For wireless broadband access systems, the problems of quality delivery are somewhat more complex than for the wireline analog. Like its wireline counterpart, the problems encountered in wireless delivery of data include, e.g., slow peripheral access, data errors, â€œdrop-outs,â€ unnecessary retransmissions, traffic congestion, out-of-sequence data packets, latency, and jitter. In addition to these problems, wireless delivery adds problems including, e.g., high inherent bit error rates (BERs), limited bandwidth, user contention, radio interference, and TCP traffic rate management. A QoS-aware wireless system is desired to address all these problems.

There are a number of ways in which users or subscribers to a data network experience difficulties. One network difficulty is due to a lack of network availability. Depending on the access technology being used, this can include a â€œmodem no-answerâ€ condition, â€œnetwork busyâ€ condition or a sudden unexpected â€œdropâ€ of a network connection. These conditions would not be described as being consistent with high QoS. Once network connectivity is achieved, slow traffic caused by congestion, local access bottlenecks, and network failures can be experienced as slow web page loading, slow file transfers, or poor voice/video quality in streaming multimedia applications. Poor quality in streaming multimedia applications can instead result from high â€œjitter,â€ or large and rapid variations in latency, leading to interruptions, distortion, or termination of session. Many different conditions can lead to actual data errors, which in some contexts can be catastrophic, such as in the file transfer of a spreadsheet. It is desirable that these problems of a data communications network be minimized or eliminated.

1. Quality

In data networking, quality usually implies the process of delivering data in a reliable and timely manner. What is reliable and timely is dependent on the nature of the traffic being addressed. These terms may include references to limitations in data loss, expectations of data accuracy, limitations of data latency variations (also known as jitter), and limitations of data retransmissions and limitations of data packet order inversions. Therefore, QoS is a complex concept, which can require a correspondingly complex mechanism to implement it.

QoS can be a relative term, finding different meanings for different users. A casual user doing occasional web browsing, but no file transfer protocol (FTP) file downloads or real time multimedia sessions may have different a different definition of QoS than a power user doing many FTP file downloads of large database or financial files, frequent H.323 video conferencing and IP telephony calls. Also, a user can pay a premium rate (i.e. a so-called service level agreement (SLA)) for high network availability, low latency, and low jitter, while another user can pay a low rate for occasional web surfing only, and on weekends only. Therefore, perhaps it is best to understand QoS as a continuum, defined by what network performance characteristic is most important to a particular user and the user's SLA. Maximizing the end-user experience is an essential component of providing wireless QoS.

2. Service

In data networking, a service can be defined as a type of connection from one end of a network to another. Formerly, this could have been further defined to be protocol specific, such as, e.g., IBM's systems network architecture (SNA), Novell's IPX, Digital's DECnet. However, it appears that TCP/IP (i.e. including user datagram protocol(UDP)) has evolved to become the overwhelming protocol of choice, and will continue to be in the foreseeable future. Therefore, service can be defined to be a particular type of TCP/IP connection or transmission. Such service types might include, e.g., FTP file transfers, e-mail traffic, hypertext transfer protocol (HTTP) traffic, H.323 videoconferencing sessions. It is desirable that a QoS mechanism deal with these differing types of service, in addition to dealing with the different types of quality as discussed previously.

3. QOS as a Mechanism

QoS can be thought of as a mechanism to selectively allocate scarce networking, transmission and communications resources to differentiated classes of network traffic with appropriate levels of priority. Ideally, the nature of the data traffic, the demands of the users, the conditions of the network, and the characteristics of the traffic sources and destinations all modify how the QoS mechanism is operating at any given instant. Ultimately, however, it is desirable that the QoS mechanism operate in a manner that provides the user with optimal service, in whatever manner the user defines it.

a. Circuit-Switched QoS

In legacy networks created primarily for voice traffic by telephone companies, data transmission was accomplished with reference to a circuit-centric definition of QoS. In this definition, QoS implied the ability to carry asynchronous (i.e. transmission of data through start and stop sequences without the use of a common clock) as well as isochronous (i.e. consistent timed access of network bandwidth for time-sensitive voice and video) traffic. Circuit-switched QoS was accomplished by dedicating an end-to-end circuit for each connection or service, whether it was voice (see

FIG. 1A

) or data. The circuit-centric QoS mechanism was simply the provision of this circuit for exclusive use by the user. Of course, this approach dedicates the circuit, all transmission channels associated with the circuit, and the transport media itself to a single user for the entire duration of the session, regardless of whether data is actually being transmitted every instant of the session. It was generally believed that only in this manner could true QoS be achieved. Therefore, traditional designs for wireless broadband access systems (see

FIG. 2A

) also used this approach, dedicating a wireless radio channel to each particular data connection, regardless of the application or whether indeed any data was being transmitted at any given moment. This circuit-centric approach to QoS is fairly expensive, in terms of the cost of the equipment, and the utilization factors for the transmission media itself.

b. Asynchronous Transfer Mode (ATM) QoS

With ATM networking, telephone companies could continue to provide a circuit-centric QoS mechanism with the establishment of permanent virtual connections (PVCs) (i.e. a virtual path or channel connection (VPC or VCC) provisioned for indefinite use) and switched virtual connections (SVCs) (i.e. a logical connection between endpoints established by an ATM network on demand based upon signaling messages received from the end user or another network) in an analogous manner to the legacy voice circuit mechanism. However, several new concepts were needed, including admission policy, traffic shaping, and mechanisms such as, e.g., leaky-buckets, in order to handle traffic that was now categorized as variable bit rate (VBR), constant bit rate (CBR), and unspecified bit rate (UBR).

Virtual circuits were to be established for data transmission sessions, again regardless of the data application or whether data was being transmitted at any given moment. Although ATM provides QoS for broadband network traffic, the underlying assumptions of ATM design include the low BER characteristic of wireline networks, not the high BER of the wireless medium. Without a recognition of the characteristics of the traffic that is being carried by the ATM mechanism and the high inherent BER of wireless, true QoS can not be provided. ATM QoS mechanisms do not address the unique challenges associated with wireless communication.

c. Packet-Switched QoS

Packet-switching is revolutionizing data communications, so conventional circuit-switch and ATM networking concepts and their legacy QoS mechanisms are in need of update. With packet-switched data communications, one cannot dedicate a circuit to a particular data communications session. Indeed, a strength of packet-switching lies in route flexibility and parallelism of its corresponding physical network. Therefore, the QoS mechanism cannot work in the same manner as the legacy circuit-centric QoS mechanism did.

Simply providing â€œadequateâ€ bandwidth is not a sufficient QoS mechanism for packet-switched networks, and certainly not for wireless broadband access systems. Although some IP-flows are â€œbandwidth-sensitive,â€ other flows are latency- and/or jitter-sensitive. Real time or multimedia flows and applications cannot be guaranteed timely behavior by simply providing excessive bandwidth, even if it were not cost-prohibitive to do so. It is desirable that QoS mechanisms for an IP-centric wireless broadband access system recognize the detailed flow-by-flow requirements of the traffic, and allocate system and media resources necessary to deliver these flows in an optimal manner.

d. Summaryâ€”QoS Mechanisms

Ultimately, the end-user experience is the final arbiter of QoS. It is desirable that an IP-centric wireless broadband access system assign and regulate system and media resources in a manner that can maximize the end-user experience. For some applications such as an initial screen of a Web page download, data transmission speed is the best measure of QoS. For other applications, such as the download or upload of a spreadsheet, the best measure of QoS can be the minimization of transmission error. For some applications, the best measure of QoS can be the optimization of both speed and error. For some applications, the timely delivery of packets can be the best measure of QoS. It is important to note that fast data transmission may not be the same as timely delivery of packets. For instance, data packets that are already â€œtoo oldâ€ can be transmitted rapidly, but by being too old can be of no use to the user. The nature of the data application itself and the desired end-user experience then can provide the most reliable criteria for the QoS mechanism. It is desired that an IP-centric wireless broadband access system provide a QoS mechanism that can dynamically optimize system behavior to each particular IP flow, and can also adapt to changes with changing network load, congestion and error rates.

4. Service Guarantees and Service Level Agreements (SLAs)

Service guarantees can be made and service level agreements (SLAs) can be entered into between a telecommunications service provider and a subscriber whereby a specified level of network availability can be described, and access charges can be based upon the specified level. Unfortunately, it is difficult to quantify the degree of network availability at any given time, and therefore this becomes a rather crude measure of service performance. It is desired that data delivery rate, error rate, retransmissions, latency, and jitter be used as measures of network availability, but measuring these quantities on a real-time basis can be beyond the capability of conventional network service providers (NSPs).

Another level of service discrimination desired by network service providers is a service level agreement (SLA) that provides for differing traffic rates, network availability, bandwidth, error rate, latency and jitter guarantees. It is desired that an IP-centric wireless broadband access system be provided that can provide for SLAs, enabling service providers to have more opportunities for service differentiation and profitability.

5. Class of Service and Quality of Service

In order to implement a practical QoS mechanism, it is desired that a system be able to differentiate between types of traffic or service types so that differing levels of system resources can be allocated to these types. It is customary to speak of â€œclasses of serviceâ€ as a means of grouping traffic types that can receive similar treatment or allocation of system and media resources.

Currently, there are several methods that can be used in wireline network devices to implement differentiated service classes. Example methods include traffic shaping, admission control, IP precedence, and differential congestion management. It is desired that an IP-centric wireless broadband access system use all of these methods to differentiate traffic into classes of service, to map these classes of service against a QoS matrix, and thereby to simplify the operation and administration of the QoS mechanism.

B. QoS and IP-Centric Wireless Environment

In a point-to-multipoint (PtMP) wireless system like the present invention, it is desirable that the QoS mechanism cope not only with wireline networking considerations, but also with considerations particular to the wireless environment. As stated earlier, it is desired that the inherent BER of wireless be handled. The high BER can require that error detection, correction, and re-transmission be done in an efficient manner. It is desired that a BER handling mechanism also work efficiently with the re-transmission algorithms of TCP/IP so as to not cause further unnecessary degradation of bandwidth utilization. An additional challenge of wireless is contention among users for limited wireless bandwidth. It is desirable that the system handle service requests from multiple users in a radio medium subject to interference and noise, which can make efficient allocation of radio bandwidth difficult.

As discussed above, the change from circuit-switched and ATM data networks to packet-switched data networks has impacted the definition of QoS mechanisms. The present invention provides a novel QoS mechanism in a point-to-multi-point IP-centric wireless system for packet-switched network traffic. In order for the system to provide optimal QoS performance, it desirable that it include a novel approach to QoS mechanisms. The use of QoS as the underlying guide to system architecture and design constitutes an important, substantial and advantageous difference of the IP-centric wireless broadband access system of the present invention over existing wireless broadband access systems designed with traditional circuit-centric or ATM cell circuit-centric approaches such as those used by Teligent and Winstar.

C. IP-Centric Wireless Broadband Access QoS and Queuing Disciplines

1. Managing Queues

Queuing is a commonly accepted tool required for manipulating data communications flows. In order for packet headers to be examined or modified, for routing decisions to made, or for data flows to be output on appropriate ports, it is desirable that data packets be queued. However, queuing introduces, by definition, a delay in the traffic streams that can be detrimental, and can even totally defeat the intent of queuing. Excessive queuing can have detrimental effects on traffic by delaying time sensitive packets beyond their useful time frames, or by increasing the RTT (Round Trip Time), producing unacceptable jitter or even causing the time-out of data transport mechanisms. Therefore, it is desired that queuing be used intelligently and sparingly, without introducing undue delay in delay-sensitive traffic such as real-time sessions.

In a wireless environment where time division multiple access (TDMA), forward error detection (FEC), and other such techniques can be necessary, it is desirable that queuing be used merely to enable packet and radio frame processing. However, in the case of real-time flows, the overall added delay in real-time traffic can preferably be held to below approximately 20 milliseconds.

The use of queue management as the primary QoS mechanism in providing QoS-based differentiated services is a simple and straight forward method for wireless broadband systems. However, wireless systems are usually more bandwidth constrained and therefore more sensitive to delay than their wireline counterparts. For this reason, it is desirable that QoS-based differentiated services be provided with mechanisms that go beyond what simple queuing can do. However, some queuing can still be required, and the different queuing methods are now discussed.

2. First in, First out (FIFO) Queuing

First in, first out (FIFO) queuing can be used in wireless systems, like wireline systems, in buffering data packets when the downstream data channel becomes temporarily congested. If temporary congestion is caused by bursty traffic, a FIFO queue of reasonable depth can be used to smooth the flow of data into the congested communications segment. However, if the congestion becomes severe in extent, or relatively long in duration, FIFO can lead to the discarding of packets as the FIFO queues are filled to capacity and the network is not capable of accepting additional packets causing discarding of packets, i.e. so-called â€œpacket-tossing.â€ Although this can have a detrimental effect on QoS in and of itself, the discarding of packets may cause future problems with traffic flow as the TCP protocol causes the retransmission of lost packets in the proper sequence, further exacerbating the problem. The problem of packet discards can be minimized by increasing the size of the FIFO buffers so that more time can pass before discards occur. Unfortunately, eventually the FIFO can become large enough that packets can become too old and the round-trip time (RTT) can increase to the point that the packets are useless, and the data connection is virtually lost.

In a wireless broadband environment, the requirement for FIFO queuing is partially dependent upon the type of RF access method being used. For time division multiple access/time division duplex (TDMA/TDD), it can be desirable that data be queued even for collecting enough data for the construction of data frames for transmission. Frequency division multiple access (FDMA) and code-division multiple access (CDMA) are not as â€œsequentialâ€ in nature as TDMA, and therefore have less of a requirement for FIFO queuing. However, generally for all wireless access techniques, noise and interference are factors that can lead to retransmissions, and therefore further delays and consequent adverse effect on QoS.

Using FIFO queuing, shared wireless broadband systems can uniformly delay all traffic. This can seem to be the â€œfairestâ€ method, but it is not necessarily the best method if the goal is to provide high QoS to users. By using different types of queue management, a much better base of overall QoS can be achieved.

3. Priority Queuing