EXHIBIT 2

Case 2:23-cv-00444-JRG Document 1-3 Filed 09/27/23 Page 1 of 23 PageID #: 42
USOO776905OB2 

(12) United States Patent (10) Patent No.: US 7,769,050 B2 

Scherzer et al. (45) Date of Patent: Aug. 3, 2010 

(54) SYSTEMAND METHOD FOR 5.835,487 A * 1 1/1998 Campanella ................ 370,316 

INTERFERENCE MITIGATION FOR 6,952.454 B1 * 10/2005 Jalali et al. ..... ... 375,260 

WIRELESS COMMUNICATION 7,042,858 B1* 5/2006 Ma et al. .................... 370,331 

7.215,659 B1* 5/2007 Chen et al. .................. 370,338 

(75) Inventors: Shimon B. Scherzer, Sunnyvale, CA 7,424,268 B2 * 9/2008 Diener et al. ................. 455,62 

(US); Patrick A. Worfolk, Campbell, 7,505.397 B2* 3/2009 Lee et al. .......... ... 370,208 

CA (US); Armin D. Haken, San 7,548,752 B2 * 6/2009 Sampath et al. ... ... 455,447 

Francisco, CA (US), Ronen vainish 2001/0030949 A1 * 10, 2001 Molno et al. ...... ... 370,329 

Sunnyvale CA (US); Subburajan s 2003/0198200 A1* 10, 2003 Diener et al. ..... ... 370,329 s s 2005/0025 101 A1 2/2005 Paneth et al. ................ 370,336 

Ponnuswamy, Scotts Valley, CA (US) 2005/0073973 A1* 4/2005 Laroia et al. ................ 370,329 

2005/0254475 A1* 11/2005 Kubler et al. ..... ... 370,338 

(73) Assignee: liter history, 2007/0025269 A1* 2, 2007 Padovani et al. ............ 370.252 

pany, L.P., s 2008.0049672 A1 2/2008 Barak et al. ....... ... 370,328 

(*) Notice: Subject to any disclaimer, the term of this 

patent is extended or adjusted under 35 * cited by examiner 

U.S.C. 154(b) by 140 days. Primary Examiner Chi H. Pham 

(21) Appl. No.: 12/109,474 Assistant Examiner Kevin Mew 

(22) Filed: Apr. 25, 2008 (57) ABSTRACT 

(65) Prior Publication Data Disclosed are systems and methods which provide interfer 

US 2008/O2274O1 A1 Sep. 18, 2008 ence mitigation by making alternative resources available 

within areas served by wireless communication links. 

Related U.S. Application Data Embodiments provide multiple channel availability in estab 

lishing wireless communication links to facilitate interfer (63) Continuation of application No. 10/730,649, filed on ence mitigation. Time domain techniques, spatial processing 

Dec. 8, 2003, now Pat. No. 7,366,202. techniques, and/or frequency domain techniques may be 

51) Int. C implemented for spectrum management. Embodiments pro 

(51) in, iMO 2006.O1 vide wireless base station configurations in which all or a 

( .01) plurality of base station sectors use a same frequency channel 

(52) U.S. Cl. ........ r 370/480; 370/328; 370/343 and/or in which each sector or a plurality of sectors use all 

(58) Field of Classification Search ......... 370/328–334, frequency channels. Multi-channel strategies may be imple 

370/480, 343, 344, 380-381,437, 442–444, mented such as to provide dynamic selection of a “best 

370/465, 468; 455/63.1, 114.2, 278.1, 296 frequency channel, to provide transmission of identical data 

See application file for complete search history. on multiple channels for combining/selection at the receiver, 

(56) References Cited and/or to provide for dividing the data for transmission on 

U.S. PATENT DOCUMENTS 

5,574,979 A * 1 1/1996 West ......................... 455, 63.1 

multiple channels. 

9 Claims, 7 Drawing Sheets 

523 

IST OF COMPATBLE 

SPATAL 

SIGNATURES 

 

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U.S. Patent Aug. 3, 2010 Sheet 1 of 7 US 7,769,050 B2 

FIG. I. 

101 IDENTIFYSPECTRUM, 

CHANNELIZATION, AND FRAME 

ARCHITECTURE TO BE USED 

PROVIDE A DEPLOYMENT 

102 CONFIGURATION PROVIDING 

COMMUNICATIONLINK 

ALTERNATIVES IN EACH 

AREA SERVICED 

IMPLEMENT TECHNIOUES FOR 

ASSIGNING AND UTILIZING 

COMMUNICATIONLINK 

ALTERNATIVES TO ACHIEVE 

DESIRED COMMUNICATIONS 

103 

FRAME FRAME 

a-A-sa a =/=a 

DOWN LINK UPLINK DOWN LINK UPLINK 

SUB-FRAME SUB-FRAME SUB-FRAME SUB-FRAME 

- 

DOWNLINK 

GROUP it 

FIG. 4A 410 

2 2 6 6 6 2 6 O-2312 4 

FRAME DURATION ADDRESSADDRESSADDRESS SEOUENCE ADDRESS FRAME g 

CONTROL MD 1 2 3 CONTROL 4. BODY 

FIG. 4B 420 

O-2047 

802.16 MAC PDU (802.16 MAC 

HEADER-i-OPTIONAL SUB-HEADERS--PAYLOAD) 

2 2 6 4 

FRAME DURATION ADDRESS 

CONTROL /ID 1 

 

 

 

 

 

 

 

 

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U.S. Patent Aug. 3, 2010 Sheet 2 of 7 US 7,769,050 B2 

| 8010BS

„D 

 

 

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U.S. Patent Aug. 3, 2010 Sheet 3 of 7 US 7,769,050 B2 

LIST OF 

COMPATIBLE 

SPATIAL 

SIGNATURES or 

523 533 

 

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U.S. Patent Aug. 3, 2010 Sheet 4 of 7 US 7,769,050 B2 

FIG. 6 FRAME i FRAME i-1 FRAME i-2 

TIME 

- RADIO ". RADIO 

-1 TURNAROUND STURNAROUND 

-1 TIME Y TIME 

CONTENTION 

DOWNLINK s ------ -1 PERIOD f's s--- 

SECTOR 4 ... ------------------ 

S= S= D = 

too i of i i 

FIG. 7 

SECTOR 1 

SECTOR2 | X | | | X | X | | X 

SECTOR 3 X X X X 

SECTOR 4 X X X X 

 

 

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U.S. Patent Aug. 3, 2010 Sheet 5 Of 7 US 7,769,050 B2 

DEGREE OF DEGREE OF 

PARALLELISM 1 PARALLELISM 4 

FIG. 8 

S1 S PARALLELSM 2 PARALLELISM3 1 S3 S4 

S12 S13 S14 S23 S24 S34 

21 2012 

SUBSCRIBER 

STATION 

BASE 210a 

STATION 

SUBSCRIBER 

STATION leaf 

201e 

 

 

 

 

 

 

 

 

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U.S. Patent Aug. 3, 2010 Sheet 6 of 7 US 7,769,050 B2 

90-N RECEIVE NEW BW REGUEST 

902 GET GROUP ID'g' 

903 RETRIEVE CORRESPONDING 

RADiO VECTOR 

904 

IS 

RADIO VECTOR ALREADY 

ACTIVE 

NO FIG. 9 

905 

REOUEST FROM 

DIFFERENT SECTOR WITH 

SAME'g? 908 

D Tavailable 

D Tiemand? 

D available 

D demand 

? 

NO U 'available 

alloc 

"demand 

906 

D availablet 

D D 'allocate'demand 

910 

D availablet 

D U D 'allocate available demand 

911 

REJECT 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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U.S. Patent Aug. 3, 2010 Sheet 7 Of 7 US 7,769,050 B2 

8 ||

ff ||

080|| 

 

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US 7,769,050 B2 

1. 

SYSTEMAND METHOD FOR 

INTERFERENCE MITIGATION FOR 

WIRELESS COMMUNICATION 

This application is a continuation of Ser. No. 10/730,649. 

filed Dec. 8, 2003, now U.S. Pat. No. 7,366,202. 

RELATED APPLICATIONS 

The present invention is related to co-pending and com 

monly assigned U.S. patent application Ser. No. 10/306,972 

entitled “Space-Time-Power Scheduling for Wireless Net 

works, filed Nov. 27, 2002, the disclosure of which is hereby incorporated herein by reference. 

TECHNICAL FIELD 

The invention relates generally to wireless communication 

and, more particularly, to interference mitigation for wireless 

communication. 

BACKGROUND OF THE INVENTION 

The use of wireless communication links, whether for 

Video, Voice, or data, have become prevalent in recent years, particularly in light of the widespread adoption of mobile 

technology, such as cellular telephones, laptop computers, 

personal digital assistants (PDAs), pagers, and the like. Wire 

less communication links are particularly desirable with 

respect to Some situations, such as to avoid obstacles associ 

ated with laying cable between communication nodes, pro viding freedom of movement, etcetera. Accordingly, wireless 

communication links have been given much consideration by communication infrastructure providers. However, deploy ing wireless communication links is not without difficulty. In 

particular, wireless spectrum is often highly regulated and 

may be prone to interference. 

Wireless broadband access has been considered quite extensively in recent years. Although multiple solutions have 

been experimented with, attempts at providing wireless 

broadband access, particularly widespread access, has gener 

ally not met with commercial Success due to inadequate eco 

nomical conditions, i.e., high cost without Sufficient demand. 

In particular, the need for licensed spectrum in which to 

provide wireless links has typically resulted in high costs to 

wireless broadband access providers. Moreover, past wireless 

broadband access Solutions have typically implemented non 

standard or application specific equipment, due to each pro 

vider developing a unique solution tailored to their particular 

Solution, circumstances, and spectrum, thereby preventing 

economies of scale and compatibility. 

Demand for Such wireless broadband access has generally 

been associated with applications and appears to be corre 

lated to at least Some degree to the cost of the service and 

equipment, the complexity of the implementation, and the 

reliability of the links. The proliferation of wired broadband 

access. Such as via cable modem and digital Subscriber line 

(DSL), is stimulating the creation of applications requiring 

relatively large amounts of bandwidth, such as music down 

loading, video streaming, multi-media presentations, etcet 

era. However, a large number of nodes desirous of imple menting Such emerging applications are not yet wired for 

broadband access and, therefore, cannot adequately access 

Such applications. 

Two related wireless technologies are beginning to gain 

acceptance in providing at least Some level of wireless broad 

band access, these being wireless technologies based on the 

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40 

45 

50 

55 

60 

65 

2 

Institute of Electronic and Electrical Engineers (IEEE) 

802.11 and 802.16 standards. The 802.11 standard is directed 

toward indoor applications and sets forth asynchronous pro 

tocols for short range communications, while the 802.16 stan 

dard is directed toward outdoor applications and sets forth 

synchronous protocols for longer range communications, 

each being operable in unlicensed spectrum Such as within 

the 2 to 11 GHz range. Implementation of such standards 

facilitates equipment cost reduction by providing for compat ibility and economy of scale. However, technologies adopting 

the foregoing standards heretofore have not adequately 

addressed the issues associated with commercial or economic 

deployment of wireless broadband access. For example, although addressing aspects Such as communication proto 

cols, the standards alone do not provide for spectrum utiliza 

tion suitable for reliable or large scale wireless broadband 

aCCCSS, 

Traditional wireless services rely upon licensed spectrum, in which the use of the spectrum is highly regulated Such that 

sources of interference are avoided, in order to provide for 

spectrum utilization Suitable for reliable or large scale access. 

However, that spectrum is expensive and is very difficult to 

obtain. Unlicensed bands, although providing a readily avail 

able and inexpensive alternative, present a cost in that the 

spectrum is open to many simultaneous uses and thus prone to 

interference leading to link degradation and even blocking. 

Such disadvantages are particularly prevalent in outdoor 

applications, where interference from uncontrolled sources 

can travel long distances, Substantially unimpeded. 

Accordingly, a need exists in the art for systems and meth 

ods providing for utilization of spectrum suitable for reliable 

and/or large scale wireless access. Particularly, a need exists 

in the art for systems and methods which mitigate interfer 

ence with respect to wireless communication links, such as 

those operable in unlicensed bands. 

BRIEF SUMMARY OF THE INVENTION 

The present invention is directed to systems and methods 

which provide interference mitigation by making alternative 

resources available within areas served by wireless commu 

nication links. Embodiments of the invention provide mul 

tiple channel availability in establishing wireless communi 

cation links to facilitate interference mitigation. For example, 

systems of the present invention may use time synchronous 

transmissions and scheduling to allow all or a plurality of 

available channels to be used throughout a service area and/or 

the network, thereby eliminate the need for cellular frequency planning according to Some embodiments. Accordingly, 

communication between nodes can be carried out over mul 

tiple channels and/or dynamically selected channels to pro vide for channel diversity. Channel diversity according to 

preferred embodiments provides strong immunity to interfer 

ence providing desired levels of quality of service (QoS) and 

enables utilization of spectrum suitable for reliable and/or 

large scale wireless access. Embodiments of the present 

invention are well suited for providing the aforementioned 

advantages with respect to the use of unlicensed spectrum in 

providing wireless communication links, and particularly in 

providing wireless broadband access using unlicensed spec 

trum. 

Preferred embodiments of the present invention implement time domain techniques (such as may include transmission 

scheduling, high rank modulation, and coding), spatial pro 

cessing techniques (such as may include grouping nodes by 

spatial attributes), as well as frequency domain techniques for 

spectrum management. Implementation of embodiments of 

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US 7,769,050 B2 

3 

the invention using Such time domain, spatial processing, and 

frequency domain techniques provides a dramatic increase of 

spectrum usage efficiency. In particular, using space/time/ 

frequency scheduling according to embodiments of the 

present invention facilitates the co-existence of many simul 

taneous communications in a particular space/spectrum 

range, without implementing traditional frequency planning 

(e.g., cellular frequency reuse planning). 

Accordingly, embodiments of the present invention pro 

vide wireless base station (BS) configurations in which all or 

a plurality of base station sectors use a same frequency chan 

nel. Moreover, embodiments of the present invention provide 

wireless base station configurations in which each sector or a 

plurality of sectors use all frequency channels. One Such 

embodiment provides a wireless broadband access network 

in which all frequency channels are used throughout the Ser 

vice area of the network, while interference associated with 

their simultaneous use is mitigated. Having availability of a 

plurality of frequency channels throughout a service area 

provides options with respect to use of a multi-channel trans 

mission strategy. For example, an ability to choose among 

frequency channels may be instrumental when a frequency 

channel is “contaminated with interference from other radi 

ating sources, such as radiating sources unrelated to a par 

ticular wireless communication network which are operating 

on frequency channels that are part of the unlicensed spec 

trum. 

Multi-channel strategies of the present invention may be 

implemented in a number of different ways. For example, a 

multi-channel strategy may provide dynamic selection of a 

“best frequency channel, e.g., based on channel quality, out 

of a plurality of available channels. Additionally or alterna 

tively, a multi-channel Strategy may provide transmission of 

identical data on multiple channels for combining/selection at 

the receiver. Such as based on cyclic redundancy checking 

(CRC) or other metrics. Similarly, a multi-channel strategy 

may provide for dividing the data for transmission on mul 

tiple channels, such as using interleaving and coding tech 

niques, with a reverse process being implemented at the 

receiver (e.g., “time? frequency coding”). Selection of a par 

ticular frequency channel using the forgoing multi-channel 

strategies, and perhaps selection of a particular multi-channel 

strategy to utilize, may depend on Such attributes as the nature 

of the transmission channel and the statistics of the interfer 

CCC. 

Embodiments implement admission control techniques to 

limit the number of communication flows that are admitted to 

the system based on various system parameters, such as QoS. capacity, bandwidth, etcetera. Additionally or alternatively, 

embodiments implement access and communication flow 

scheduling based on space, time, and/or frequency param 

eters. 

Space/time/frequency scheduling according to an embodi 

ment of the invention employs a two-tier scheduling strategy. 

A first tier scheduler may preferably be executed in a central 

control RF manager unit (RFMU) and assign transmission 

time period opportunities, perhaps at a relatively 'slow pace.” 

to wireless nodes (WNs) of the base stations to support groups 

of subscriber stations (SSs). Such transmission time period opportunities may be assigned by an RFMU based upon 

relative spatial conditions between WNs, uncontrolled inter 

ference levels, signal propagation levels, traffic loads, QoS 

metrics, and/or the like. A second tier Scheduler may prefer ably be executed at each BS and provide real time scheduling, 

such as based on traffic load per individual SS and/or QoS metrics. According to preferred embodiments, each WN 

serves SSs within the subscriber groups allocated to the WN 

4 

by the RFMU scheduler and provides real time scheduling 

among the SSS of an assigned group. The foregoing approach 

allows high efficiency while minimizing the processing 

power utilized in implementing Such scheduling. 

The foregoing has outlined rather broadly the features and 

technical advantages of the present invention in order that the 

detailed description of the invention that follows may be 

better understood. Additional features and advantages of the 

invention will be described hereinafter which form the sub 

10 ject of the claims of the invention. It should be appreciated 

15 

25 

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55 

60 

65 

that the conception and specific embodiment disclosed may 

be readily utilized as a basis for modifying or designing other 

structures for carrying out the same purposes of the present 

invention. It should also be realized that such equivalent 

constructions do not depart from the invention as set forth in 

the appended claims. The novel features which are believed to 

be characteristic of the invention, both as to its organization and method of operation, together with further objects and 

advantages will be better understood from the following 

description when considered in connection with the accom 

panying figures. It is to be expressly understood, however, 

that each of the figures is provided for the purpose of illus 

tration and description only and is not intended as a definition 

of the limits of the present invention. 

BRIEF DESCRIPTION OF THE DRAWINGS 

For a more complete understanding of the present inven 

tion, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in 

which: 

FIG. 1 shows a high level flow diagram setting forth steps 

for implementing wireless broadband access according to an 

embodiment of the present invention; 

FIG. 2 shows an embodiment of a wireless broadband 

access system topology as may be implemented according to 

the steps of FIG. 1; 

FIG. 3 shows an 802.16 like frame structure as may be 

implemented according to an embodiment of the invention 

for Scheduled communication with groups of Subscriber sta 

tions; 

FIG. 4A shows a typical IEEE 802.11 over-the-air frame; 

FIG. 4B shows an embodiment of an over-the-air frame 

which may be used with respect to wireless broadband access 

system of FIG. 2 according to an embodiment of the inven 

tion; 

FIG. 5 shows partial ordering of subscriber station groups based on a spatial signature of the group according to an 

embodiment of the invention; 

FIG. 6 shows a frame layout of allocations across 4 sectors 

as may be implemented using a scheduler of the present 

invention; 

FIG. 7 shows the subscriber station groups of FIG. 5 from 

the viewpoint of base station sector 1: 

FIG. 8 shows schedules of active radios vectors corre 

sponding to the subscriber station groups of FIG. 5: 

FIG. 9 shows a flow diagram setting forth operation of a 

reservation manager in servicing bandwidth requests accord 

ing to one embodiment of the invention; 

FIG. 10 shows communication front end circuitry adapted 

to provide post data selection according to one embodiment 

of the invention; 

FIG. 11 shows communication front end circuitry adapted 

to provide time/frequency coding according to one embodi 

ment of the invention; and 

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US 7,769,050 B2 

5 

FIG. 12 shows a portion of a wireless broadband access 

network operable in an unlicensed band according to one 

embodiment of the invention. 

DETAILED DESCRIPTION OF THE INVENTION 

Directing attention to FIG. 1, a high level flow diagram setting forth steps for implementing wireless broadband 

access according to an embodiment of the present invention is 

shown. Having determined that wireless broadband access is 

to be provided, spectrum to be used, and channelization and 

frame architectures to be implemented in establishing com 

munications via wireless communication links in the selected 

spectrum are identified (step 101). A configuration for 

deploying wireless broadband infrastructure to provide com 

munication link resource alternatives throughout a service 

area is provided (step 102). Techniques are implemented 

(step 103) for assigning and utilizing wireless communica 

tion link alternatives to achieve desired communication 

objectives, such as to provide a desired QoS as may be mea 

sured by bandwidth, delay, jitter, loss rate, and/or other 

attributes. 

Where unlicensed spectrum is to be utilized in providing 

information communication, such as for implementing wire 

less broadband access, the Sources of interference are not 

limited primarily to devices in the communication network 

(referred to herein as internal interference sources), but may include any number of devices external to the communication 

network (referred to herein as external interference sources). Cooperative operation among network devices, e.g., synchro 

nization and spatial Scheduling, may be used to address inter 

ference associated with internal interference sources. How 

ever, Such techniques are ineffective at addressing 

interference associated with external interference sources. 

Moreover, typical implementations of synchronization and 

spatial scheduling rely upon predefined and inflexible chan 

nel reuse plans permeating the communication network in 

order to provide for multi-channel transmission approaching 

an optimized use of resources. 

Providing communication link resource alternatives, such 

as multiple channels, throughout the service area according to 

embodiments of the present invention provides communica 

tion link diversity, Such as in the form of channel usage diversity, and thus may be utilized to provide robust commu 

nication operations. In an embodiment wherein multiple 

channels are made available throughout all portions of a ser 

Vice area, particular channels for use in a communication link 

may be dynamically selected by each side of the communi 

cation link, Such as based upon a continuous channel activity 

evaluation, to mitigate interference associated with external 

interference sources. Additionally or alternatively, transmis 

sion of information to a particular network device may be 

executed simultaneously or quazi-simultaneously on mul 

tiple channels to mitigate interference associated with exter 

nal interference sources. Spatial segregation, e.g., directional 

and/or narrow beam antenna configurations, may be utilized 

according to embodiments to increase channel activity vari 

ability options with respect to the various network devices 

deployed in the communication network. According to one 

embodiment, spatial scheduling is implemented by creation 

of network device groupings to optimize channel usage while 

mitigating interference. 

In operation according to the foregoing, network devices 

may use forward error correction (FEC), automatic request for repetition (ARQ), re-tries, fragmentation, data rate adjust 

ment, variable modulation techniques, and/or the like when 

communicating over the selected channel or channels. 

10 

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25 

30 

35 

40 

45 

50 

55 

60 

65 

6 

Implementing robust communication operations accord 

ing to embodiments of the present invention as described 

above may utilize different channels in the uplink and down 

link communication links, due to the expectation that inter 

ference conditions may be appreciably different in each link 

direction. 

FIG. 2 illustrates an embodiment of a wireless broadband 

access system topology as may be implemented according to 

the steps of FIG. 1. The embodiment of wireless broadband 

access system 200 of FIG. 2 includes a base station (BS) 

having a plurality of wireless nodes (WNs), shown as WNs 

210a-212a associated with sector 1, 210b-212b associated 

with sector 2, 210C-212c associated with sector 3, and 210d 

210d associated with sector 4, providing wireless communi 

cation links throughout a service area to a plurality of Sub 

scriber stations (SSs), shown as 201a-201m. It should be 

appreciated that embodiments of the invention may comprise 

any number of WNs and/or sectors determined to provide Suitable communication link resource alternatives throughout a service area. 

The WNs of the illustrated embodiment may comprise any 

number of configurations, such as wireless access points 

(APs), routers, Switches, etcetera, as may comprise CPE, 

service provider equipment, and/or the like. WNs are prefer 

ably associated with relay communication links. According 

to one embodiment, WNs utilized according to the invention 

each operate on a different frequency channel, and thus a 

plurality of WNs are provided with respect to sectors provid 

ing multiple frequency channels therein as shown. Radio 

frequency management unit (RFMU) 220 is shown coupled 

to WNs 210a-210d, 2.11a-211d, and 212a-212d to provide scheduling control as described in detail below. 

The SSs of FIG. 2 may comprise any number of user or 

customer premise equipment (CPE) configurations, such as 

personal computer systems (e.g., 201c), personal digital 

assistants (PDAS) (e.g., 201h), wireless access points (e.g., 

201a), routers, Switches, etcetera, enabled to communicate 

via wireless links. As illustrated in FIG. 2, SSs may be asso 

ciated with terminal network links, such as may be associated 

with termination equipment, and may be associated with 

relay communication links, such as are associated with wire 

less access points, routers, Switches, etcetera. 

The foregoing devices may provide information to and 

between any number of devices and networks, such as to 

provide access to server 251 via local area network (LAN) 

250 by any or all of SSs 201a-201 m, WNs 210a-210d., 211a 

211d, and 212a-212d, and/or RFMU 200. Similarly, net 

works, such as the public switched telephone network 

(PSTN) 230 and Internet 240, may provide communication 

links to a variety of devices, as is well known in the art. 

Although RFMU 220 is illustrated coupled to one BS (here 

BS 221) for simplicity, wireless broadband access network 

200 may comprise a plurality of BSs and RFMU 220 may be 

coupled thereto for coordinating the operation thereof. Like 

wise, although a single RFMU is illustrated in FIG. 2, 

embodiments of the present invention may implement a plu 

rality of RFMUs, if desired. For example, a plurality of 

RFMUs may be disposed in wireless broadband access net 

work 200 to provide a distributed processing configuration in 

which scheduling control processing is distributed among 

such RFMUs. Additionally or alternatively, scheduling func 

tionality of an RFMU of embodiments of the invention need 

not be provided by a discrete management unit. For example, 

scheduling functionality of an RFMU as described herein 

may be disposed within one or more BSs of wireless broad 

band access network 200. 

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US 7,769,050 B2 

7 

Any of the foregoing network devices (e.g., SSs, WNs, 

BSs, RFMUs) may comprise processor-based systems con 

figured to provide operation as described herein. For 

example, one or more of SSs 201a-201 m, WNs 210a-210d. 

211a-211d, and 212a-212d, BS 221, and RFMU 220 may comprise a general purpose processor-based system having a 

central processing unit (CPU) (e.g., from the Intel PENTIUM 

family of processors), memory (e.g., random access memory 

(RAM), read only memory (ROM), magnetic storage, optical 

storage, etcetera), and appropriate input/output devices (e.g., 

network interface card (NIC), display monitor, keyboard, pointing device, modem, microphone, speakers, printer, 

etcetera) operable under control of an instruction set to pro vide desired operating functions. 

Although particular communication link types are illus 

trated in FIG. 2, it should be appreciated that the link types 

shown are exemplary to aid in the understanding of the 

present invention and are not illustrative of any limitation of 

the application of the concepts of the invention. For example, 

although shown using wireline communication between BS 

221 and RFMU 220, between BS 221 and the PSTN, between 

BS 221 and Internet 240, between BS 221 and LAN 250, 

between LAN 250 and server 251, and between SS 201e and 

SS 201f any form of suitable communication link may be 

implemented with respect to the present invention. Accord 

ingly, wireless links (e.g., links the same as those illustrated 

between WNs and SSs, cellular links, bluetooth links, etcet 

era), optic links (e.g., fiber optic, free space optic links, etcet 

era), network links (e.g., LAN, metropolitan area network 

(MAN), wide area network (WAN), intranet, extranet, the 

Internet, the PSTN, etcetera) and/or the like may be utilized as 

desired. 

Similarly, the link paths shown are exemplary to aid in the 

understanding of the present invention and are not illustrative 

of any limitation of the application of the concepts of the 

invention. Accordingly, communication between network 

devices is not restricted to the particular paths shown. For 

example, communication links (wireless or otherwise) may 

be established between WNs 210a-210d., 211a-211d, and 

212a-212d to provide backhauling or through connectivity, if 

desired. Additionally, SSs 201a-201m are not restricted to the 

particular communication links illustrated and, therefore, 

may establish communication links with one or more of WNs 

210a-210d., 211a-211d, and 212a-212d different than illus 

trated (as well as one or more WNs of other BSs (not shown)). 

BS 221 of FIG. 2 is shown having a sectorized configura 

tion, e.g., directional antenna beams or other radiation pattern 

controls are utilized to provide isolation or separation of 

wireless communications within Sub-areas associated with 

each sector. Specifically, the illustrated embodiment includes 

sectors 1 through 4, each providing approximately 90' 

azimuthal service area coverage with respect to each of WNs 

210a-210d., 211a-211d, and 212a-212d. Of course, different 

numbers and sizes of sectors, or other service area portions, 

may be implemented or no sectors utilized, according to 

embodiments of the present invention. 

A preferred embodiment of wireless broadband access sys 

tem 200 implements a plurality of frequency division mul 

tiple access (FDMA) channels. For example, frequency chan 

nels f-f may be implemented for providing simultaneous 

and Substantially non-mutually interfering communications 

with respect to a plurality of SSs 201a-201m. The foregoing 

frequency channels may further be divided into slots or indi 

vidual time slices (e.g., time division multiple access 

(TDMA)), thereby providing further channelization for non 

mutually interfering communications. Of course, additional 

or alternative channelization techniques may be implemented 

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according to embodiments of the present invention, Such as 

code division multiple access (CDMA), if desired. 

Various techniques may be implemented in establishing 

downlink (e.g., transmission from a WN to a SS) and uplink 

(e.g., transmission from a SS to a WN) communication iso 

lation according to embodiments of the invention. For 

example, frequency division duplexing (FDD) may be imple 

mented wherein different frequency division channels are 

used in the downlink and uplink communication links (e.g., 

fl-fa for downlink communication and f-f for uplink communication). However, preferred embodiments of the 

invention implement time division duplexing (TDD), 

wherein downlink communication is isolated from uplink communication in time. A split between downlink and uplink portions of a communication sequence may be asymmetric, 

perhaps dynamically adjusted to accommodate a current 

downlink and uplink communication capacity balance, thus 

implementing an ATDD technique. 

Embodiments of the present invention provide for making 

alternative channels available within each WN sector, e.g., multiple ones of frequency channels f-f may be utilized 

with respect to one or more WN sectors to provide alterna 

tives with respect to channels used in establishing communi 

cation links with particular SSs. However, preferred embodi 

ments of the present invention do not implement a frequency 

reuse plan (e.g., a typical cellular frequency reuse plan) which 

limits the reuse of Such frequency channels in adjacent/ad joining sectors or even adjacent/adjoining BSs. Instead, 

embodiments of the present invention allow for use of the 

same frequency channel (e.g., any off-f) in adjacent/adjoin 

ing sectors and/or adjacent/adjoining BSs, as will be better 

understood from the discussion which follows. A preferred embodiment of the present invention allows for use of all the 

frequency channels (e.g., all off-f) in adjacent/adjoining 

sectors and adjacent/adjoining BSS. It should be appreciated 

that, given the nature of unlicensed spectrum communica 

tions being Subject to external interference, the use of mul 

tiple channels (preferably all channels) in each sector of the 

communication network facilitates channel usage diversity according to the present invention, thereby providing robust 

communication operation. 

Embodiments of the present invention provide robust inter 

ference mitigation, such as with respect to interference asso 

ciated with external interference sources, using availability of 

multi-channel service through a wireless broadband access 

network. For example, configurations implementing the con 

cepts of the present invention provide for adaptive dynamic 

channel selection such that the best channel out of several 

available channels may be selected for providing a commu 

nication link between particular network node pairs. Addi 

tionally or alternatively, embodiments may implement post 

data selection, Such that transmission of identical data on 

multiple channels is provided for combining/selection at the 

receiver based on metrics such as cyclic redundancy code 

(CRC). Similarly, embodiments may implement time/fre 

quency coding. Such that data is divided for transmission on 

multiple channels after interleaving and coding for combin 

ing/decoding at the receiver based on a reverse process. 

Selection of one or more Such interference mitigation tech 

nique to implement with respect to particular communica 

tions may depend upon a number of factors, such as the nature 

of the transmission channel, the interference statistics, etcet 

era. Control with respect to the foregoing interference miti 

gation techniques may be provided by centralized and/or 

decentralized management algorithms, such as those of 

RFMU 220, WNs 210a-210d, 211a-211d, and 212a-212d, 

and/or SSS 201a-201m. 

Case 2:23-cv-00444-JRG Document 1-3 Filed 09/27/23 Page 13 of 23 PageID #: 54
US 7,769,050 B2 

A post data selection interference mitigation technique implemented according to one embodiment provides for mul 

tiple copies of the data to be simultaneously transmitted over 

multiple channels. Accordingly, when the multiple copies of 

the data arrive at the destination network node, a single, valid 

copy of the data may be sorted out of the multiple transmis 

sions. For example, data validation techniques, such as CRC, 

may be utilized with respect to the multiple copies of the data 

to identify a valid data set for use by the network node. 

Directing attention to FIG. 10, communication front end 

circuitry 1000, as may be implemented with respect to any of 

SSs 201a-201 m and WNs 210a-210d., 211a-211d, and 212a 

212d. is shown adapted to provide post data selection accord 

ing to one embodiment. The illustrated embodiment includes 

transceiver 1010 wherein N radios (shown as radios 1011a 

1011n) and N MACs (shown as wMACs 1012a-1012n) are 

operable in synchronization with respect to different fre 

quency channels. Each of radios 1011a-1011n is simulta 

neously transmitting/receiving frames of the same length and 

including the same data, albeit on a different frequency chan 

nel, according to one embodiment. 

In providing for transmission of data in a post data selec 

tion interference mitigation technique according to one 

embodiment, frames of variable lengths may arrive at frame 

aggregator/de-aggregator unit 1030 for packing into fixed 

length frames. According to a preferred embodiment, the 

packing process maintains the main bodies and MAC headers 

of the original frames while encapsulating the frames into a 

new “packed frame' with new MAC and PHY headers and 

CRC trailers. Control and frame selector unit 1020 may receive the fixed length frames from frame aggregator/de 

aggregator unit 1030 and pass the frames in parallel to each of 

wMACs 1012a-1012n for transmission by corresponding ones of radios 1011a-1011n. 

In providing for reception of data in a post data selection 

interference mitigation technique according to one embodi 

ment, packed frames are received by each of radios 1011a 

1011n and are passed to corresponding ones of wMACs 

1012a-1012n. The received frames are passed to control and 

frame selector unit 1020, wherein control and frame selector 

unit 1020 selects a “good frame, such as based on its CRC. 

The selected packed frame may then be passed to frame 

aggregator/de-aggregator unit 1030 for de-aggregation to its 

original components (e.g., the incoming frames discussed 

above). 

To provide for efficiencies in transmission, acknowledge 

ments can be cumulative, Such as by providing an ACK frame 

as part of the payload of the frames being transmitted at the 

opposite direction. When one of the original frames aggre 

gated into a packed frame is found to be erroneous, a bit map 

may be used to indicate this failure so that only this particular 

frame will be re-sent with a later packed frame. 

Post data selection interference mitigation techniques, Such as the foregoing example, capitalize on the fact that 

interference on the channels is typically highly un-correlated. 

For example, using one frequency channel for transmission of 

data (e.g., one radio/MAC pair for the communication link) 

the frame error probability may be predicted or measured, 

such as may be on the order of a probability of 0.1 (10%). 

However, the use of a second frequency channel for simulta 

neous transmission of the same data (e.g., two radio/MAC 

pairs for the communication link) does not decrease the frame 

error probability by half, but rather results in an order of 

magnitude decrease in probability due to the un-correlated 

nature of the probability of the two channels experiencing interference. Accordingly, in the foregoing example, using a 

second frequency channel for simultaneous transmission of 

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the same data the frame error probability may be on the order 

of a probability of 0.01 (1%). Although it may appearinitially 

that implementation of the foregoing post data selection inter 

ference mitigation technique will cause greater interference 

to other transmissions, the interference to other transmission 

is expected to be greatly reduced. Specifically, the frame error 

probability reduction for the exemplary two channel trans 

mission is equivalent to gain that is much larger than x2, 

hence the interference to other transmissions can be reduced 

by more than the x2 channel utilization increase. For 

example, the reduction in probability of frame-error-rate 

(FER) allows faster transmission of data, using the channels 

for shorter periods, and/or the use of less transmission power. The foregoing post data selection interference mitigation 

technique is well suited to use of the multiple available chan 

nels of embodiments of a wireless broadband access network 

according to embodiments of the present invention. More 

over, post data selection interference mitigation techniques as 

described herein can readily be implemented using existing 

hardware. However, the use of multiple channels to simulta 

neously transmit the same data according to post data selec 

tion interference mitigation embodiments described herein 

results in relatively limited efficiency. For example, when 

more than one channel is interference free, the maximum 

throughput is limited to a single channel's performance. If, 

due to distance for example, use of a channel provides for 

only 15 Mb/s to be transmitted, a post data selection based 

system might only provide 15 Mb/s of throughput regardless 

of the number of channels which are simultaneously capable 

of this data rate. Such a lack of efficiency may be particularly 

exacerbated in situations, such as where large distances 

between transceivers are supported, such as by allowing low 

data rate (e.g., 256 Kb/s). 

A time/frequency coding interference mitigation technique 

implemented according to one embodiment provides for effi 

cient usage of the available spectrum, and consequently may 

be utilized to increase the effective distance between network 

nodes. Directing attention to FIG. 11, communication front 

end circuitry 1100, as may be implemented with respect to 

any of SSs 201a-201m and WNs 210a-210d, 2.11a-211d, and 

212a-212d. is shown adapted to provide time/frequency cod 

ing according to one embodiment. The illustrated embodi 

ment includes transceiver 1110 wherein N radios (shown as 

radios 1111a–1111n) and N MACs (shown as wMACs 

1112a-1112m) are operable in synchronization with respect to 

different frequency channels. Each of radios 1111a–1111n is 

simultaneously transmitting/receiving frames of the same 

length, albeit on a different frequency channel and including differing information, according to one embodiment. 

Similar to operation of frame aggregator/de-aggregator 

unit 1030 discussed above, frame aggregator/de-aggregator unit 1150 provides packing and unpacking of frames. Accord 

ingly, packed frames are passed between frame aggregator/ 

de-aggregator unit 1150 and encoder/decoder 1140. Encoder/ 

decoder 114 of a preferred embodiment provides block 

encoding using various encoding/decoding techniques. Such 

as convolutional, turbo codes etcetera. Preferably, the coding 

rate implemented is variable. Such as from no coding to /10 

rate or higher. If there is not enough data for the fixed size 

frame, additional null bits may be concatenated as needed 

according to one embodiment. Encoded frames are passed 

between encoder/decoder 114 and interleaver/deinterleaver 

1130 for interleaving/deinterleaving data for simultaneous 

communication via N radios (shown here as radios 1111a 

1111n), such that each radio transmits or receives part of the 

desired information. Splitting techniques implemented according to the present invention may comprise dividing the 

Case 2:23-cv-00444-JRG Document 1-3 Filed 09/27/23 Page 14 of 23 PageID #: 55
US 7,769,050 B2 

11 

aggregated frame into N and adding headers. Of course, other 

splitting techniques may be implemented in addition to or in 

the alternative to the foregoing, if desired. Similar to opera 

tion of control and frame selector unit 1020 discussed above, 

control and frame distribution unit 1120 may arbitrate frames 

between frame interleaver/deinterleaver unit 1030, passing 

the frames in parallel between each of wMACs 1112a-1112n 

of transceiver 1110. Of course, the foregoing is but one 

embodiment of a frequency/time coding system, and alterna 

tive embodiments may be utilized according to the present 

invention. 

As with the post data selection interference mitigation techniques discussed above, acknowledgements can be 

cumulative to provide efficiencies. For example, an ACK 

frame may be provided as part of the payload of the frames 

being transmitted at the opposite direction. 

It should be appreciated that time/frequency coding inter 

ference mitigation techniques as discussed above provide advantages in bandwidth scalability and higher efficiency. 

For example, when more channels are “clean” (e.g., experi 

ence less interference and therefore have a high channel qual 

ity), more information can be transmitted. Where 2 channels 

are clean, and each channel is capable of 15 Mb/s, approxi 

mately 30 Mb/s can be transmitted using the time/frequency 

coding interference mitigation technique described above. 

Accordingly, when the channels are not being Substantially interfered, a system implementing time/frequency coding 

interference mitigation techniques may transmit N times 

more data than a system implementing post data selection 

interference mitigation techniques. 

The coding rate implemented by a time? frequency coding 

embodiment may be adjusted based on bit error rate. For 

example, if one channel is clean and the other channel expe riences a 10% bit error rate, a coding rate providing /2 error 

correction rate may be invoked. In this example, the system 

may still carry approximately 15 Mb/s (with no re-try). Addi 

tionally or alternatively, channels experiencing higher levels 

of interference (poorer quality channel) can be discovered 

throughout operation by monitoring transmission statistics, 

Such that less data is allocated to the poorer quality channels 

Such that bit error rate can be reduced to require less coding, thereby increasing system efficiency. 

Another interference mitigation technique, referred to 

herein as dynamic channel selection (DCS), may be utilized 

with respect to the multiple channels provided according to 

embodiments of the invention to provide increased efficiency. Dynamic channel selection may be implemented utilizing 

any of a number of communication frontend circuitry, includ 

ing communication front end circuitry 1000 of FIG. 10 and 

1100 of FIG. 11, having the ability to communicate using a 

channel selected from a plurality of channels. According to 

embodiments of the DCS interference mitigation technique, a 

transceiver transmits data on a selected channel and uses 

communication link feedback, Such as ARQ or re-try rates, as 

a metric for determining when to switch to a different chan 

nel. For example, if a re-try rate threshold (or other metric 

threshold) is exceeded, the transceiver may coordinate a 

change to another channel. Additionally or alternatively, if a 

re-try rate threshold (or other metric threshold) is exceeded, 

the transceiver may increase the level of fragmentation (i.e., 

making the fragments shorter), reduce the data rate, increase 

the interval between fragments, and/or the like to improve the 

error rate. If the foregoing does not result in appreciable 

decrease in the re-try rate (or other metric), such as to fall 

below a threshold amount, the transceiver may coordinate a 

change to another channel. Channels may be selected by 

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monitoring link metrics, such as communication quality, and/ 

or based upon a channel selection hierarchy. 

A system employing DCS is preferably able to rapidly 

Switch network nodes from a low quality channel (high inter 

ference level) to a higher quality channel (lower interference 

level). Scheduler functionality may therefore maintain 

knowledge of each channels condition. Channel selection 

will preferably take into account the channel traffic load as 

well as the channel condition such that the channel selection 

decision is based on combined traffic load and interference 

conditions. 

In operation according to one embodiment, a WN is the 

decision maker with respect to channel selection. A SS may 

report channel conditions to an associated WN (e.g., using special measurement reports), the WN may combine this 

information with channel conditions measurements per 

formed by the WN and add traffic load information to produce 

channel selection decisions. If a channel selection decision is 

that a channel is to be switched, the WN preferably coordi 

nates the process with the affected SS. 

In operation according to an alternative embodiment, each 

receiver (e.g., each SS receiver and each WN receiver) selects 

its “preferred’ channel for receiving information communi 

cation, Such as based upon an evaluation of the channel activ 

ity at the respective receiver. Such an embodiment provides 

for the use of different uplink and downlink channels (e.g., an 

SS may transmit on one channel whereas the corresponding 

WN transmits to that SS on another channel) as may be 

desirable in particular situations because interference condi 

tions may be different at each communication link termina 

tion point. In implementing the foregoing embodiment, the 

radios used in a communication link may switch from chan 

nel to channel at the TDD frame boundaries and splitting points. 

According to a preferred embodiment, SSs have sufficient 

time between their assigned time slots to scan other available 

channels (e.g., in the exemplary implementation, the 3 sector 

channels in addition to the sector channel then in use by the 

SS). According to one embodiment, a WN may allocate time 

slots in which a SS is to scan channels. Such scanning of 

channels may comprise reception of packets transmitted on 

the downlink by the WN. These packets may be “beacon 

packets, data packets directed to other SSS etcetera. Accord 

ing to a preferred embodiment, a SS collects information such 

as RSSI, CRC errors, physical layer convergence procedure 

(PLCP) errors, and/or the like, on a perchannel and perpacket 

basis. For each channel the SS may sum frame error reports and RSSI values to produce a FER and average RSSI per 

channel. The channel-FER and channel-RSSI info may be 

grouped into channel condition reports and sent to an associ 

ated WN, such as in time slots allocated by the WN. 

According to a preferred embodiment, BSs have receivers 

tuned substantially full time to each frequency channel. Such 

that no channel scanning need be implemented. Accordingly, 

in this embodiment a BS can collect FER and RSSI statistics 

on all channels all the time. In case of no uplink activity, the 

WN may allocate special probing time slots where associated 

SSs can send packets from time to time to allow the WN to 

collect channel statistics. Where uplink power control is 

implemented, it is expected that SSs will be received by an 

associated WN with similar signal strength, allowing a WN to 

aggregate uplink packets into a combined channel-FER and 

channel-RSSI report. Additionally, WNs preferably operate 

to monitor downlink queues and the amount of allocated 

uplink bandwidth to estimate channel load, for use in making 

DCS decisions. 

Case 2:23-cv-00444-JRG Document 1-3 Filed 09/27/23 Page 15 of 23 PageID #: 56
US 7,769,050 B2 

13 

In making a determination as to whether to switch a SS 

from one channel to another, DCS algorithms of a preferred 

embodiment scheduler functionality considers channel con 

ditions, channel traffic load, Scheduling efficiency, and/or the 

like. Channel traffic load may be estimated through such 

information as the average delay or latency experienced in 

transmission of data packets, the Volume of data packets transmitted in a immediately preceding window, the average 

Volume of data packets transmitted, the allocated time slots, 

and/or the like. Channel conditions and traffic load may be 

expressed as: 

FER:(FER WN+FER SS)*K 

where FER WN is the frame error rate on the channel as 

measured by the WN, FER. SS is the frame error rate on the 

channel as measured by the SS, and K is a proportion factor 

coefficient as may be determined by simulation, empirical 

data, etcetera. According to a preferred embodiment, if chan 

nel conditions are lower than a predetermined channel 

switching threshold (e.g., CHANNEL SWITCH THRESH 

OLD), DCS algorithms will start channel-switching process. 

According to a preferred embodiment, the DCS algorithms 

will examine the traffic load on any potential target channels 

and select the one with Sufficient quality and minimum traffic 

load for the SS channel change. 

The foregoing interference techniques may be effectively implemented using scheduling techniques for coordinating 

the use of alternative resources, such as multiple channels. 

Communication synchronization and spatial scheduling is 

preferably implemented according to embodiments of the 

present invention in order to facilitate effective multi-channel 

communication. Accordingly, all transmissions using the 

communication channels available in the system (e.g., fre 

quency and time division channels) are coordinated and 

scheduled according to embodiments of the present inven 

tion, except perhaps transmissions in specific contention 

slots, such as may be allocated by a WN scheduler. Schedul 

ing with respect to each WN sector is preferably independent, 

except for group restrictions imposed by a scheduler of the 

present invention, such as that of an RFMU, and except for an 

ATDD split, where implemented. 

Preferred embodiments of the present invention utilize 

unlicensed spectrum, Such as that in the 2-11 GHZ range in the 

United States. Although subject to interference by unrelated 

communications in the same band, Such unlicensed spectrum is freely available and its use according to the present inven 

tion facilitates an economical wireless broadband access 

Solution. A further advantage of utilization of such unlicensed 

spectrum is the existence of standards, such as the IEEE 

802.16 standard, with respect to its use and the availability of 

components and equipment operable therewith. 

Such standards often set forth protocols including channel 

ization and frame architectures for use with respect to par ticular bands of unlicensed spectrum. For example, the IEEE 

802.16 protocols implement time division multiple access 

(TDMA) operation, such that transmission time is divided 

into frames that are split into a downlink Sub-frame and an 

uplink sub-frame wherein the frame size and split point can be 

adjusted as needed. Each sub-frame is divided into slots or 

individual time slices. Various aspects of such channelization 

and frame architectures may be adapted for use according to 

the present invention, thereby providing economies in devel 

opment and implementation of a wireless broadband access 

system. 

Moreover, various manufacturers produce transmitters, 

receivers, and other equipment operable in Such unlicensed 

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spectrum bands using Such standardized channelization and 

frame architectures. Accordingly, economies may be realized 

through taking advantage of the availability of Such equip 

ment. 

For example, embodiments of the present invention may 

implement an 802.16 like frame structure for scheduled com 

munication with groups of SSS, wherein groups of slots are 

allocated for specific SSs in the downlink and uplink sub 

frames, as shown in FIG. 3. The size and time location of the 

group within the frames may be determined by Scheduling 

processes of the present invention. The foregoing frame struc 

ture provides advantages Such as facilitating grouping of mul 

tiple transmissions to allow for a common, single preamble at 

the downlink (e.g., for the entire sub-frame), thereby elimi 

nating the need for preamble per SS. Additionally, efficien 

cies may be realized with respect to other overhead or control 

aspects. Such as by implementing ARQ through “piggy-back 

ing the acknowledge character (ACK) messages in the slots 

coming from the opposite direction. A cumulative ACK Strat 

egy can additionally or alternatively be employed, further 

enhancing link efficiency. Moreover, there is no need to wait 

for an ACK before sending a new data, according to embodi 

ments, thereby providing transmission efficiency as the “ACK 

round-trip' could be a significant portion of the link time line. 

Accordingly, embodiments of the invention implement a 

medium access control (MAC) common part Sub-layer (re 

ferred to herein a wMAC), which is modeled after the 802.16 

MAC. For example, a wMAC of the present invention may 

Support management interfaces as defined in the 802.16 stan 

dard. Additionally or alternatively, message exchange 

between a SS and WN may comprise those defined in the 

802.16 standard, although the wMAC may not support all 

Such defined messages and/or may support additional or alter 

native messages. Of course, different MAC configurations 

may be utilized according to embodiments of the present 

invention to achieve the above goals. 

A preferred embodiment of the present invention supports 

the IEEE 802.11 physical layer (PHY), although such an 

embodiment may impose some restrictions on PHY overhead 

(preamble, PLCP. etcetera) and addressing methods. Accord 

ingly, an over-the-air frame of wireless broadband access 

system 200 may substantially correspond to an 802.11 frame, as shown in FIGS. 4A and 4B wherein frame 410 illustrates a 

typical 802.11 frame and frame 420 illustrates an embodi 

ment of a frame which may be used with respect to wireless 

broadband access system 200. However, an 802.11 compliant 

MAC may not be able to successfully decode the contents of 

a wMAC frame of the preferred embodiment. Such a frame 

configuration is desired according to embodiments of the 

invention in order to facilitate ready use of equipment and 

infrastructure in providing wireless broadband access by wireless broadband access system 200, even if other systems using equipment conforming to the same standards are not 

communicatively compatible with wireless broadband access 

system 200. 

The downlink MAC with respect to wireless broadband 

access system 200 of the illustrated embodiment provides point-to-multipoint operation. This MAC operation accord 

ing to embodiments of the invention is independent of the 

actual topology of the network (point-to-point, point-to-mul 

tipoint, mesh). Accordingly, a wMAC of preferred embodi 

ments of the invention Supports mesh and/or point-to-point 

extensions in addition to or in the alternative to providing for 

point-to-multipoint operation. 

The foregoing point-to-multipoint operation, wherein ser 

Vice to multiple SSS is provided, is leveraged according to 

embodiments of the present invention to provide an addi 

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US 7,769,050 B2 

15 

tional source of diversity gain, that being “time diversity.” Using time diversity techniques according to embodiments of 

the invention, when a SS is unacceptable channel conditions 

(e.g., unacceptable C/I). Such as a result of fading or increased 

interference, the BS can serve another SS experiencing more 

acceptable channel conditions. This way, the BS can select 

the best channel/SS to be served among a given SS group (assuming the conditions are randomly changing and all SSS 

will be served in turn). Operation according to the foregoing preferably implements fast response and may be imple 

mented as part of a scheduler executed by a WN. 

Quality of service (QoS) definition and control is prefer 

ably an integral part of the wMAC according to embodiments 

of the invention. Although the 802.16 standard provides a 

QoS model, it should be appreciated that the 802.16 standard 

does not specify a particular scheduling algorithm to achieve 

a desired QoS. Accordingly, various wMAC functions, such 

as scheduling, ARQ, fragmentation, packing, and/or the like, 

are utilized according to a preferred embodiment to work 

together to provide a desired QoS. 

A QoS model typically involves two major functions, those 

being admission control and Scheduling. Admission control 

limits the number of information flows (as can be thought of 

as active communication links) that are admitted to the sys 

tem based on various system parameters. Scheduling is a 

real-time function that schedules communications so that the 

QoS can be guaranteed and misbehaving information flows 

can be shaped. 

A scheduler of an embodiment of the present invention 

provides traffic shaping and packet scheduling in a configu 

ration which may be easily integrated into a reasonably pow 

erful CPU. A scheduler framework implemented according to 

a preferred embodiments of the invention provide admission 

control and Scheduling functionality. Embodiments of a 

scheduler framework implemented according to the present 

invention further provide the ability to meet service level 

agreements (SLAs), a frame-based queuing model meeting various fairness requirements, a work-conserving scheduler 

with rate control, a load-sharing scheduler for excess band 

width, and/or congestion control and packet dropping. 

It should be appreciated that, unlike a wire-line scheduler 

that is responsible for scheduling frames in a fixed capacity 

channel, a wireless scheduler often copes with a varying 

channel capacity, Such as due to interference, link environ 

ment, fading, shadowing, etcetera. However, the use of 

frames (e.g., TDD frames) may be utilized according to the 

present invention to provide flexibility in optimizing the com 

plexity of scheduling, such as by considering available chan 

nel capacity and making assignments on a frame basis. 

According to embodiments of the invention, a scheduler 

treats both uplink and downlink queues the same, although allocating appropriate contention slots in the uplink. Traffic 

may flow simultaneously between WNs and SSs in both 

uplink and downlink directions whether on the same channel 

in different sectors or on different channels in the same sector, 

wherein network devices using the same channel in the same 

sector are queued for serial traffic flow. 

A scheduler according to embodiments of the invention 

provides assignment of communication attributes in addition 

to channels. For example, a preferred embodiment provides 

for transmit power assignment. Such an embodiment may be 

implemented where it is determined that it is advantageous 

for various network devices to transmit with different power 

levels, such as to have WNs transmit with different power 

levels to the different SSs depending on their distance from 

the WN. Transmit power assignment may be asymmetric, 

Such as by having the SSS power levels remain constant (e.g., 

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chosen so that the WNs receive at least a minimum signal strength from all SSS while dynamically assigning transmit 

power with respect to WNs). 

Preferred embodiment schedulers according to the present invention implement a hierarchical scheduling approach to 

channel assignment. A first level of such a hierarchical sched 

uling approach may operate to assign channels to groups of 

network devices, such as based upon spatial aspects of the 

network devices. A second level of such a hierarchical sched 

uling approach may operate to allocate the assigned channels 

among the network devices of a group or groups. This hier 

archical scheduling approach lends itself particularly well to 

a configuration in which particular scheduling functionality is 

provided centrally and other scheduling functionality is pro 

vided in distributed fashion. 

For example, centrally deployed RFMU 220 (FIG. 2) may provide channel assignments as among groups of network 

devices, perhaps even determining the groupings of the net 

work devices for Such channel assignments. Such a central 

ized system is able to analyze demand and capacity and 

distribute assignment of resources (e.g., assignment of fre 

quency channels, adjust a split between downlink and uplink portions of a communication sequence, etcetera) to optimize 

network communications. BS 221, or perhaps each of WNs 

210a-210d., 211a-211d, and 212a-212d, upon receiving grouping and channel assignments from RFMU 220, may 

allocate the assigned channels (e.g., assign particular fre 

quency and/or time slot channels) among the network devices 

or groups associated therewith. Such a distributed approach is 

able to implement a network Scheduling plan without requir ing exceptional processing power to be implemented with 

respect to any particular aspect of the network. In particular, 

the aforementioned distributed scheduler functionality may 

be utilized to manage and coordinate the allocation of time 

between WN/SS pairs, such as to avoid the need to respond to 

dynamic variations of hundreds of SSs directly by the fore 

going central Scheduler functionality. 

As described in detail in the above referenced patent appli cation entitled “Space-Time-Power Scheduling for Wireless 

Networks, scheduling may be utilized as an alternative to 

interference isolation by frequency planning. Aggressive use 

of Scheduling facilitates the availability and use of a single 

channel throughout a service area. Carrying this concept to an 

extreme, embodiments of the invention provide for availabil 

ity and use of all channels throughout a service area. 

Preferred embodiment operation of a scheduler includes 

the ability to form SS groups (as discussed in detail below), 

wherein a set of SSS in a SS group possess similar spatial characteristics (e.g., each member of a given SS group has 

similar spatial distance (wherein here spatial distance 

between two network nodes is defined as a value that is 

proportional to the path loss between them) from a corre 

sponding WN) and are serviced by a same WN. Accordingly, in operation according to an embodiment of the invention, 

WNs 210a-210d., 211a-211d, and 212a-212d continuously or 

periodically collect signal reception level (e.g., received sig 

nal strength indicator (RSSI)) and/or other channel quality 

measurements for ones of SSs 201a-201 m, and provide this 

information and traffic load information to scheduler func 

tionality. Using this information, a first scheduler function 

may make coarse scheduling decisions to allocate channels 

(time/frequency) across groups, essentially comprising selec 

tion of a subset of radios (radios being used herein to refer to 

a receiver, transmitter, or transceiver operable to provide communications using a particular frequency channel) which 

may be utilized for simultaneous transmission. A second 

scheduler function may make finer levels of scheduling deci 

Case 2:23-cv-00444-JRG Document 1-3 Filed 09/27/23 Page 17 of 23 PageID #: 58
US 7,769,050 B2 

17 

sions to distribute the allocated channels between members of 

the SS group. Such as to meet individual QoS requirements or 

targets. 

According to a preferred embodiment the coarse scheduler 

functionality is provided in a centralized implementation 

(e.g., comprising algorithms operable upon RFMU 220 of 

FIG. 2) and the fine scheduler functionality is provided in a 

distributed implementation (e.g., comprising algorithms 

operable upon a plurality network BSs, such as BS 221 of 

FIG.2). In operation according to one embodiment, the group 

members include network nodes for which communication 

links will be established with a particular WN using a par 

ticular frequency channel. Determination of such groups may 

include identification of groups which may communicate 

simultaneously, groups which may not communicate simul 

taneously, a number of frames (or length of time) for which 

the group assignment is to be implemented, a split between 

downlink and uplink portions of the communication 

sequence to be implemented, etcetera. Such group informa 

tion is provided to the corresponding WN for assignment of 

particular time slots to the network nodes of an assigned 

group to provide individual communications meeting desired 

link metrics. Assignment of time slots to individual network 

nodes of a group may be based upon channel quality metrics, 

network node priorities, data type priorities, round-robin or 

fairness allocations, traffic demand, etcetera. 

Channel quality estimation as utilized in a scheduler of the 

present invention (e.g., scheduler functionality distributed in 

BSs to make scheduling decisions between SSs of a SS group 

to meet individual QoS targets) may implement any number 

of channel quality metrics. For example, FER or packet error 

rate measures may be utilized as an indication of link quality. 

External interference power (I) (interference power associ 

ated with external interference sources) on the channel and 

the signal power (C) from a given WN may be translated into 

an equivalent FER by calculating a carrier to interference 

(C/I) ratio and using a lookup table for conversion to an FER 

value. Additionally or alternatively, FER may be measured 

directly, Such as by sending probing frames for collecting 

frame error statistics. Of course, channel quality metrics use 

ful according to the present invention are not limited to the 

foregoing. 

According to one embodiment of the invention information 

with respect to an average FER on a channel may be deter 

mined using information about the rate at which the channel 

quality changes. The rate at which channel quality changes 

may be determined by using external interference power (I) 

measurement (or using probing frames as discussed above). 

For example, two time periods may be defined, such as a short 

period TS (e.g., a few frame lengths) and a long period TL 

(e.g., approximately one hundred frame lengths), for use 

determining channel quality changes using the aforemen 

tioned external interference power (I) measurement or prob ing frames. Every TL Seconds K measurements may be taken 

TS seconds apart such that measurements are taken in bursts. 

The closely spaced measurements may be utilized to provide 

information regarding fast changes in the channel (e.g., 

instantaneous channel quality changes) while the different 

bursts are utilized to provide information regarding slow 

changes in the channel (e.g., channel quality change trends). 

According to one embodiment of the invention, the fore 

going channel quality change measurements are converted 

into an equivalent FER and the geometric mean of the FER 

values in each burst is computed. Additionally or alterna 

tively, an average of these FER values, over some relatively longtime period (e.g., 100*TL), may be calculated (the result 

of the latter calculation referred to herein as FER LINK). 

5 

10 

15 

25 

30 

35 

40 

45 

50 

55 

60 

65 

18 

FER LINK represents the effective FER on the link when K 

retries are used to transmit each packet. When the channel 

quality changes slowly, FER LINK equals the true average 

FER. However, when the channel quality changes quickly, 

FER LINK will be smaller (perhaps very much smaller) than 

the true average FER. Calculation of FER LINK provides a 

useful indication of channel quality as affected by external 

interference sources and, thus, may be utilized in a total 

channel quality measurement implemented according to 

embodiments of the invention which takes known or predict 

able interfering Sources into account. 

It should be appreciated that, when multiple network nodes 

are transmitting on the same channel, internal interference is 

generated. Accordingly, for any combination of transmitting 

WNs and a given SS a carrier to interference plus noise ratio 

(CINR) may be computed with respect to the SS. This CINR 

value may be translated into an equivalent FER (the result of 

the latter translation referred to herein as FER INT). The 

total FER experienced by the SS will be approximately the 

sum of the FER due to external interference (FER LINK) and 

the FER due to self-interference (FER INT), assuming that errors in transmission due to external interference and inter 

nal interference occur independently and that the FER is 

Small. Accordingly, a measurement of total link quality may be calculated using the following equation: 

FER=FER LINK--FER INT. 

Of course, additional or alternative techniques for determin 

ing channel quality and/or definitions of channel quality may 

be implemented according to the present invention. For 

example, according to one embodiment, system receivers are 

used to directly evaluate the activity on a channel to measure 

energy time density, average power, transmission duration 

statistics, and/or interval between transmission duration sta 

tistics. 

Using the foregoing signal reception level and/or other 

channel quality measurements, network node grouping may 

be implemented according to embodiments of the invention 

to assign channels among the groups and facilitate simulta 

neous communication links throughout the network. In pro viding network node grouping according to one embodiment, 

the nodes of the wireless access network are organized in a 

tree, wherein branches of the network node tree begin with a 

WN connected to the RFMU and leafs may comprise SSS 

serving one or more end users. As shown in FIG. 2, the branch 

level WNs may service one or more SSs. 

To aid in understanding the concepts of a scheduling pro 

cess implemented according to the present invention, an 

exemplary embodiment wherein a total of 8 possible sector 

spatial groupings of network nodes will be described. Spe 

cifically, assuming the case of no interference between chan 

nels, all channels are available in all sectors, and 4 sectors are 

provided with respect to each BS, 8 possible groups with 

which a SS may be associated comprise: Transmission only in 

the sector under consideration for a given channel (1 combi 

nation), wherein 1 radio is active in the space; Transmission in 

the sector under consideration together with transmission in 

one of the other 3 sectors (3 combinations), wherein 2 radios 

are active in the space; Transmission in the sector under 

consideration together with transmission in two of the other 3 

sectors (3 combinations), wherein 3 radios are active in the 

space; and Transmission in all 4 sectors simultaneously (1 

combination), wherein 4 radios are active in the space. How 

ever, it should be appreciated that the invention is not limited 

to the foregoing number of network node groupings. 

Case 2:23-cv-00444-JRG Document 1-3 Filed 09/27/23 Page 18 of 23 PageID #: 59
US 7,769,050 B2 

19 

It should be appreciated that the example set forth herein is 

with reference to a single channel for simplicity in explaining 

the concepts of the present invention. Preferred embodiments 

of the present invention implement a plurality of channels 

(most preferably all channels) in each portion of a service 

area. Accordingly, the concepts set forth herein with respect 

to a single channel would be repeated for each Such channel 

according to embodiments of the invention. 

A 4-bit binary vector (e.g., vector (b1, b2. b3, b4), wherein 

b1-b4 represent each of 4 bits) indicating interfering/non 

interfering radios, as may be determined by RSSI measure 

ments, can be utilized to represent the above 8 groups. In 

describing vectors indicating non-interfering radios, radios 

will be referenced herein with sector ids corresponding to the 

sector numbers in which they are implemented (see FIG. 2 for 

sector numbers which are labeled clockwise from 1 to 4). 

Using this nomenclature, radio R1 represents a radio of WN 

210a operating in sector 1 for a given channel. Considering 

for a moment a SS operable in sector 2 the SS is serviced by radio R2 (a radio of WN210b operating in sector 2 for a given 

channel) and indicated by marking bit b2 of the binary vector 

(e.g., setting bit b2 to “1” to indicate RSSI with respect to R2 

is above a particular threshold). Other bits of the binary vector 

(b1, b3, and b4) indicate the status of radios in other sectors 

with respect to the SS. For example, the SS receiving the 

signal of radio R1 (a radio of WN210a operating in sector 1 

for the given channel) may be indicated by marking bit b1 of 

the binary vector (e.g., setting bit b1 to “1” to indicate RSSI 

with respect to R1 is above a particular threshold), and the SS 

receiving the signal of radio R4 (a radio of WN 210d operat 

ing in sector 4 for the given channel) may be indicated by marking bit b4 of the binary vector (e.g., setting bit b4 to “1” 

to indicate RSSI with respect to R4 is above a particular 

threshold). Likewise, the SS not receiving the signal of radio 

R3 (a radio of WN 210c operating in sector 3 for the given 

channel) may be indicated by marking bit b3 of the binary 

vector (e.g., setting bit b3 to “0” to indicate RSSI with respect 

to R3 is below a particular threshold). Accordingly, the binary 

vector (1,0, 1, 1) may be determined to apply with respect to 

the particular SS. It should be appreciated that in the forego 

ing example, a binary vector bit of “O'” indicates non-inter 

fering communication with respect to a particular radio Such 

that communications can be activated in parallel to R2, so that 

the BS may serve more than one SS simultaneously using a 

particular frequency channel when SSS are grouped appro priately. 

Applying the concepts of the foregoing example to each 

SS, SSS having similar spatial characteristics are assigned a 

same binary vector. Therefore, such a binary vector may be 

utilized in deriving a “spatial signature' with respect to each 

corresponding SS, wherein such a spatial signature provides 

information with respect to the availability of radios for 

simultaneous use. According to one embodiment of the 

present invention, the bits of a binary vector not associated 

with the sector in which the SS is disposed are flipped, such 

that a “1” becomes a “0” and a “0” becomes a “1,” to form a 

spatial signature. For example, in the foregoing example, the 

SS is disposed in sector 3, therefore bit b3 of the binary vector 

remains unchanged but bits b1, b2, and b4 are flipped such 

that the spatial signature (0,1,1,0) is determined. The appear 

ance of 1's in the spatial signature indicates that the corre 

sponding radios, here radios R2 and R3, can be active in 

parallel to service two SSs in sectors 2 and 3. 

It can be seen from the above that preferred embodiment 

spatial signatures provide information with respect to the WN 

radios operable upon a same frequency channel which may be 

simultaneously operated to provide communication links 

10 

15 

25 

30 

35 

40 

45 

50 

55 

60 

65 

20 

with respect to groups of SSS. Accordingly, schedules of 

active radios may be derived from the spatial signatures. Such 

that groups of compatible spatial signatures are associated 

with each schedule of active radios. The schedules of active 

radios, and accordingly the spatial signature groups associ 

ated therewith, may be assigned a weight Wiwhereie {1,2,3, 4} and Wi-Wi+1. According to a preferred embodiment, a 

RSSI analysis process running at RFMU 220 identifies each 

SS with an optimal group, based upon group weighting, 

whereby RFMU 220 attempts to increase the size of the 

highest-weighted group in the order of W4 to W1. An optimal grouping strategy assigns SSS to one of the eight groups so as 

to guarantee a given C/I at the receivers while maximizing the 

probability for parallel transmissions. 

Directing attention to FIG. 5, a partial ordering of the 8 

possible groups each SS may be identified with (and corre 

spondingly the schedule of active radios), according to the 

exemplary embodiment described herein, is shown. FIG. 5 

demonstrates the partial ordering of SS groups based on the 

spatial signature of the group. For a particular schedule of 

active radios S, a spatial signature OS may be computed, 

wherein the group with spatial signature O is the most restric 

tive group compatible with S. 

In the illustration of FIG. 5, the upper portion of each box 

provides the particular schedule of active radios ordered and 

the lower portion of each box provides a list of the spatial 

signatures which are compatible with the schedule of active 

radios. As can be readily appreciated from FIG. 5, schedule of 

active radios S1=(0, 0, 0, 1) is compatible with all 8 spatial 

signatures as shown in box 511. This schedule of active radios 

is most restrictive with respect to simultaneous transmission 

and therefor is weighted as W4. Schedules of active radios 

S=(0, 0, 1, 1), S(0, 1, 0, 1), and S (1,0,0,1) are com 

patible with 4 of the 8 spatial signatures as shown in boxes 

521, 522, and 523, respectively. These schedules of active 

radios are less restrictive with respect to simultaneous trans 

mission and therefore are weighted as W3. Schedules of 

active radios S=(0, 1, 1, 1), S6=(1, 0, 1, 1), and S=(1, 1, 0, 1) are compatible with 2 of the 8 possible spatial signatures as 

shown in boxes 531,532, and 533, respectively. These sched 

ules of active radios are even less restrictive with respect to 

simultaneous transmission and therefore are weighted as W2. 

Schedule of active radios Ss=(1,1,1,1) is compatible with 1 

of the 8 possible spatial signatures as shown in box 541. This 

schedule of active radios is least restrictive with respect to 

simultaneous transmission and therefore is weighted as W1. 

Accordingly, the partial ordering represented by the arrows of 

FIG. 5 indicates a greater than relationship, showing all the 

groups of spatial signatures (O) that are compatible with each 

schedule of active radios (S). This partial ordering is very powerful and gives a lot of 

flexibility to the BS to utilize allocated time efficiently, allow 

ing for a more flexible use of group scheduling. Specifically, 

a BS can choose a SS for which to schedule transmissions, 

either on uplink or on downlink, from all the groups whose 

spatial signature O satisfies the condition (S&& O)=S. For 

example, if the central scheduler chooses “1001 as the vector 

S to activate radios, then any group having “1XX1 (wherein 

“X” is a “don’t care' bit) as the spatial signature will qualify 

to access the channel. 

In initially identifying a network node (WN, SS) with a SS 

group according to one embodiment, each SS is temporarily 

allocated on a unit vector group in the sector of the SS (e.g., spatial signature (1, 0, 0, 0) for a SS disposed in sector 1) in 

both the uplink and downlink directions, without any explicit allocations. Thereafter, the SS may exchange Some special 

packets with the corresponding WN, in order to learn the 

Case 2:23-cv-00444-JRG Document 1-3 Filed 09/27/23 Page 19 of 23 PageID #: 60
US 7,769,050 B2 

21 

spatial distance of the SS and move it to a better group to 

increase the multiplexing factor in the space. In assigning a 

proper spatial signature for a given SS according to one 

embodiment, network nodes in the wireless broadband access 

network in addition to a network node providing a then active 

communication link with the SS measure received signal strength for both the uplink and downlink transmissions for 

this SS. This process determines a suitable spatial signature 

vector for the SS, hence classifying the SS into one of the 8 

groups. 

Furthermore WNs and SSs may continuously monitor the 

status of the channel between each WN and SS pair. A channel 

Switching algorithm may be utilized for changing the channel 

for SSS experiencing poor channel conditions. After changing 

the channels a BS preferably temporarily assigns this SS to a 

default unit vector group corresponding to a spatial signature 

compatible only with radio communication on the newly assigned channel in the sector of the SS (e.g., spatial signature 

(1, 0, 0, 0) for a SS disposed in sector 1). Thereafter, network 

nodes measuring the received signal strength and the RFMU 

RSSI process of a preferred embodiment assigns the SS sta 

tion to a proper group according to the rules described above. 

As described above with respect to an embodiment of the 

present invention, a central scheduler may provide a semi 

static schedule over a period of time where network nodes 

(WN, SS) are afforded the opportunity to transmit data in the 

downlink and the uplink. An assumption according to one 

embodiment is that during this period of time neither signifi 

cant RF changes nor significant bandwidth requirements have 

changed (e.g., the bandwidth demands of individual groups have not changed). Another assumption according to one 

embodiment is that the network nodes of a wireless broad 

band access network are synchronized. Such as using Syn 

chronous clocks, external clock signals (e.g., global position 

ing system (GPS) clock signals), and the scheduler advertises 

schedules with reference to this common time. 

It should be appreciated that a scheduler may choose com 

binations of various schedules of active radios S to implement in any particular period of time, e.g., a frame, in order to 

provide access to each network node, regardless of its spatial signature, having a demand for communication capacity. 

However, a portion of the particular period of time allocated 

to any Such schedule of active radios may be based upon the 

number of network nodes served in a corresponding spatial signature grouping, the amount of communication demand 

served by a particular schedule of active radios, etcetera. One 

or more network nodes may be associated with spatial signa 

ture groups serviceable by multiple ones of the schedules of 

active radios, thereby allowing such network nodes to be 

serviced in multiple groups, such as to provide a desired link 

capacity thereto while still providing at least a minimum link 

capacity to all active network nodes. 

The group allocation process may attempt to optimize 

group assignments to improve the throughput while minimiz 

ing the total interference among the concurrent transmis 

sions. Accordingly, a preferred embodiment scheduler 

attempts to allocate time to a particular group as a single 

contiguous burst to increase the efficiency. However, this 

condition may be subject to other constraints imposed on the 

scheduler. 

Directing attention to FIG. 6, a frame layout of allocations 

across 4 sectors as may be implemented using a scheduler of 

the present invention is shown. Frame duration of the frame 

illustrated in FIG. 6 is subdivided into four main regions, including a frame header (preferably fixed length), a down 

link period (preferably variable length), an uplink period 

(preferably variable length), and a contention period (fixed or 

10 

15 

25 

30 

35 

40 

45 

50 

55 

60 

65 

22 

variable). As discussed above, a central Scheduler may specify a spatial signature to be processed by the BSs of the 

wireless broadband access network. As illustrated in the 

embodiment of FIG. 6, each schedule of active radios vector 

has designated bit positions that correspond to a specific WN 

in a specific sector. Further, each schedule of active radios 

vector is preferably associated with a time offset reference to 

the start of a frame, thereby enabling WNs to activate radios 

according to a specified pattern. Accordingly, for each frame, 

WNs traversing through this list of schedule of active radios 

vectors in the order they specified, choosing members (i.e. 

SSs) from the eligible groups to grant the access during each 

time interval, areassured a minimum of self-interference. The 

scheduler preferably produces commands enabling the net 

work nodes to start transmissions during the appropriate downlink periods and/or uplink periods at defined time 

boundaries. 

According to an embodiment of the invention, it is 

expected that the network nodes will know traffic demands 

associated therewith. For example, a SS may know the indi 

vidual subscriber's traffic requirements that are to be chan 

neled in the uplink to a corresponding WN. Similarly, a WN 

may know the bandwidth requirements of each individual SS 

that it serves in the downlink. Such network nodes may map these aggregate bandwidth requirements to a standard scale 

(e.g., a number of time slots), for use by a scheduler in 

assigning capacity. A network node, for example, may oper 

ate to decide if rising bandwidth requirements can be locally 

resolved without sending an explicit request to a central 

scheduler, Such as by analyzing the use of the time slots 

allocated to the network node, analyzing the use of the time 

slots utilized by network nodes in the same spatial signature 

group or groups, etcetera. If the network node decides to 

request more capacity (e.g., additional time slots), the node 

preferably computes the additional bandwidth requirements 

in the standard Scale (e.g., how many more time slots to be 

demanded in addition to the already allocated slots) to meet 

the aggregate bandwidth requirements. Information with 

respect to additional bandwidth demand may be forwarded 

the central scheduler of one embodiment by the network node 

desirous of the increased communication capacity, perhaps with information specifying a maximum time delay between 

successive bandwidth allocations for the network node. The 

central scheduler may operate to attempt to dispense Succes 

sive grants to the requested node, preferably satisfying the 

aforementioned delay constraint without degrading the allo 

cations associated with other network nodes. Of course. QoS. minimum bandwidth, and other guaranteed link metrics asso 

ciated with ones of the network nodes may suggest that Such 

time slot allocations take precedent even where degradation 

of particular other network node links will result. Network 

nodes preferably keep track of the usage of allocated time 

slots. In operation according to a preferred embodiment, if a 

network node detects that the time slots allocated thereto is 

above that needed, the network node may communicate with 

the central scheduler of one embodiment to release one or 

more Such time slots. As can be appreciated from the forego 

ing, in a preferred embodiment network nodes and Scheduler 

functionality, such as a central scheduler operable upon 

RFMU 220 (FIG. 2) communicate to request bandwidth for a 

specific group (WN/SS->RFMU), release bandwidth from a 

specific group (WN/SS->RFMU), inform the success/failure 

of previous allocations (WN/SS->RFMU), and allocate/de 

allocate requested bandwidth (RFMU->WN/SS). 

The allocation and release of time slots can be considered 

as managing a pool of time slots. According to a preferred 

embodiment, a scheduler and the network nodes coordinate to 

Case 2:23-cv-00444-JRG Document 1-3 Filed 09/27/23 Page 20 of 23 PageID #: 61
US 7,769,050 B2 

23 

respond rapidly in assigning time slots to serve rising band 

width requirements and to respond more slowly in releasing 

time slots associated with falling bandwidth requirements. This fast rise/slow decay time slot assignment technique 

avoids oscillation between allocation and de-allocation due to 

short-term bandwidth fluctuations. 

As discussed above, network nodes in each sector may be 

organized into one or more of 8 potential groups by spatial 

signatures as shown in FIG. 5. Directing attention to FIG. 7, 

the aforementioned 8 groups are shown from the viewpoint of 

sector 1, wherein radio R1 of sector 1 is always active with 

different combinations of other radios. Similar radio activa 

tion plans can be made for each sector by considering the 

spatial signature groups, as shown in the table below wherein 

all the combinations for activating radios possible in the 

exemplary embodiment are set forth. 

Sector 1 Sector 2 Sector 3 Sector 4 

OOO1 OO10 O1 OO 1OOO 

OO11 OO11 O101 1001 

O101 O110 O110 1010 

1001 1010 1100 1100 

O111 

1011 

1101 

1111 

O111 

1011 

1110 

1111 

O111 

1101 

1110 

1111 

1011 

1101 

1110 

1111 

A review of the bit patterns shown in the foregoing table 

reveals that there are 16 unique patterns, meaning that in the 

exemplary embodiment there are 16 possible radio activation 

patterns across the network (it being appreciated that the null 

vector (0, 0, 0, 0), wherein all radios are silent, is not shown). 

Therefore, these 16 bit patterns represent the schedules of 

active radios vectors S that are available to be communicated 

to BSs facilitating BSs choosing possible groups of SSS based 

upon spatial signatures. 

The 15 schedules of active radios vectors (omitting the null 

vector) are shown in FIG. 8, wherein the subscripts corre 

spond to sectors of the active radios. These consecutive 

unique values can be easily organized in an array (radio vector 

array) with each value uniquely identifying a data structure 

describing the properties of a particular radio pattern. This 

data structure can hold various properties, such as whether the 

radio pattern is active or not, how long this specific radio 

pattern is active during a frame (i.e. how many slots are 

assigned on the corresponding group), etcetera. 

According to a preferred embodiment, a reservation man 

ager (RM), such as may be operable as a part of the central 

ized scheduler, assigns some time period Talemand (e.g., an 

integer multiple of slot length) for each of the demanded 

groups for the uplink and/or the downlink, and actives the 

corresponding radio vector. Thereafter, network nodes may 

make explicit requests for downlink and uplink bandwidth 

depending on the current requirements. 

Operation of a RMinservicing bandwidth requests accord 

ing to one embodiment is shown in the flow diagram of FIG. 

9. The flow diagram of FIG.9 begins at step 901, wherein the 

RM receives a new bandwidth request. At step 902, a groupid 

of the network node making the bandwidth request is 

obtained, such as from the bandwidth request itself. The radio 

structure for the identified group is retrieved at step 903, such 

as by using the group id to directly access this structure. 

At step 904 it is determined if the radio pattern associated 

with the retrieved radio structure is already active. If the radio 

pattern corresponding to the request is not active then this is 

10 

15 

25 

30 

35 

40 

45 

50 

55 

60 

65 

24 

a type of request to activate a new group. Since this request 

demands allocation in time, it may or may not successful 

depending on the residual time. Accordingly, if the radio 

pattern is not already active, then processing proceeds to step 

908 wherein a determination is made as to whether the time 

slots in the downlink which are available are greater than the 

time slots in the downlink which are demanded. If the time 

slots in the downlink which are available are greater than the 

time slots in the downlink which are demanded, then the 

bandwidth request is granted at step 907. However, if the time 

slots in the downlink which are available are not greater than 

the time slots in the downlink which are demanded, process ing proceeds to step 909 wherein a determination is made as 

to whether the time slots available in the downlink plus the 

timeslots available in the uplinkare greater than the time slots 

in the downlink which are demanded. If the time slots avail 

able in the downlink plus the timeslots available in the uplink 

are greater than the time slots in the downlink which are 

demanded, then the bandwidth request is granted at step 907, 

perhaps including adjustment of a split between downlink and 

uplink portions of a communication sequence. However, if 

the time slots available in the downlink plus the time slots 

available in the uplink are not greater than the time slots in the 

downlink which are demanded, then the bandwidth request is 

rejected at step 912. 

If at step 904 it is determined that the radio pattern is 

already active, then processing proceeds to step 905 wherein 

a determination is made as to whether the bandwidth request 

is from a different sector with the same group id. If the radio 

pattern is already active and if the request came from one of 

the exiting sectors then this is a type of request to increment 

the size of the allocation of already activated group. Since this 

request demands allocation in time, it may or may not suc 

cessful depending on the residual time. Accordingly, if the 

bandwidth request is determined not to be from a different 

sector with the same group id, then processing proceeds to 

step 908, the operation of which is described above. However, 

if it is determined that the bandwidth request is from a differ 

ent sector with the same groupid, then processing proceeds to 

step 906. 

At step 906, a determination is made as to whether the time 

slots allocated are greater than the time slots demanded. If the 

already reserved time period Talloc for a particular group is 

greater than the demanded time Tdemand for that particular 

group, then the request does not require any explicit alloca 

tion in time. If Talloc less than Talemand then the RM should 

to adjust the already allocated time interval for this group. 

Accordingly, if the time slots allocated are greater than the 

time slots demanded then processing proceeds to step 907, 

wherein the bandwidth request is granted. However, if it is 

determined that the time slots allocated are not greater than 

the time slots demanded, then processing proceeds to step 

910. At step 910 a determination is made as to whether the 

time slots available in the downlink plus the time slots allo 

cated in the downlink are greater than the time slots 

demanded in the down link. If the time slots available in the 

downlink plus the time slots allocated in the downlink are 

greater than the time slots demanded in the down link, then 

processing proceeds to step 907, wherein the bandwidth 

request is granted. However, if the time slots available in the 

downlink plus the time slots allocated in the downlink are not 

greater than the time slots demanded in the down link, then 

processing proceeds to step 911. At step 911 a determination 

is made as to whether the time slots available in the downlink 

plus the time slots allocated in the downlink plus the time 

slots available in the uplink are greater than the time slots 

demanded in the downlink. If the time slots available in the 

Case 2:23-cv-00444-JRG Document 1-3 Filed 09/27/23 Page 21 of 23 PageID #: 62
US 7,769,050 B2 

25 

downlink plus the time slots allocated in the downlink plus the 

timeslots available in the uplinkare greater than the time slots 

demanded in the downlink, then processing proceeds to step 

907 wherein the request for bandwidth is granted, perhaps including adjustment of a split between downlink and uplink 

portions of a communication sequence. However, if the time 

slots available in the downlink plus the time slots allocated in 

the downlink plus the time slots available in the uplink are not 

greater than the time slots demanded in the downlink, then 

processing proceeds to step 912 wherein the request for band 

width is rejected. 

Pseudocode for implementing aspects of the foregoing 

flow diagram are set forth below, wherein: 

T a -aiiable 'P is total bandwidth available for allocations in the 

downlink; 

Ti(g) is bandwidth already allocated for the group, i.e., 

g’, in the downlink: 

Taeman f(g) is bandwidth requested by group g; and 

T. is total bandwidth available for allocations in the uplink. 

Pseudocode 

//available bandwidth plus already allocated bandwidth is enough to 

satisfy the new demand 

F (Tavailabi. "Tallocat, (g) Taemand (g)) 

Allocation is successful 

ELSE 

i? available bandwidth plus already allocated bandwidth is not enough to 

satisfy the new demand 

f/try to burrow from the uplink period 

F (Tavailabi. "Tallocat, "Tavailabi. Tamand) 

Allocation Successful 

ELSE 

No available bandwidth in the system to meet the demand 

//available bandwidth is enough to satisfy the new demand 

F (Tavailabi. Taemand) 

Allocation is successful 

ELSE 

i? available bandwidth is not enough to satisfy the new demand 

// try to burrow from the uplink period 

F (Tavailablet Tavailable Taemand) 

Allocation Successful 

ELSE 

No available bandwidth in the system to meet the demand 

It should be appreciated that the formulas shown with 

respect to the pseudocode and the flow diagram of FIG. 9 are 

with respect to the downlink. However, these formulas of the 

illustrated embodiment are equally applicable to the uplink. 

Although embodiments have been described above with 

respect to a SS communicating with a particular BS in estab 

lishing information communication, it should be appreciated 

that the concepts of the present invention are applicable to 

multiple BS communication operations. Specifically, the pro 

vision of alternative resources with respect to the BSs of a 

wireless broadband access network of a preferred embodi 

ment provides flexibility with respect to scheduling and inter 

ference mitigation using multiple BSS with respect to a par 

ticular SS. 

To extend the multi-channel operation across the whole 

network embodiments of the present invention may extend 

the time/space/frequency scheduling throughout the network 

Such that all BSs transmissions are coordinated (e.g., extend 

ing the above two tier scheduling to the entire network). 

Alternatively, multi-channel operation may be extended 

across the whole network by leaving the different BSs unco 

ordinated, although this approach may lead to some degrada 

tion as a result of transmission collisions. As a middle ground 

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60 

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26 

between full coordination and no coordination, embodiments 

of the invention may implement limited coordination, Such as 

by using different transmit power levels on different channels 

such that sectors facing each other will use different transmit 

power levels for the same channel. The latter 2 of the above 

coordination techniques may be preferred according to par 

ticular embodiments because of their relative simplicity. In 

these situations, the other BSs may be treated as any other 

un-controlled interference source. To guarantee acceptable 

performance, each WN’s activity may be controlled such that 

the transmission duty cycle on each channel/sector will be 

limited (e.g. <25%). This limitation can be successfully 

achieved as a result of the scheduling process described 

above, since system capacity Substantially increases and a 

Smaller percentage of the time is needed to Support the desired 

service. If the transmission duty cycle is kept relatively mod 

erate, transmission failures due to collisions can be easily 

fixed by re-transmission (ARQ). 

Directing attention to FIG. 12, a portion of a wireless 

broadband access network operable in an unlicensed band 

implementing aspects of the forgoing embodiments is shown. 

As can be appreciated from the detail shown in FIG. 12, the 

illustrated embodiment implements 802.11 related compo 

nents as building blocks to achieve the functionality 

described above. Specifically, BS 221 of the illustrated 

embodiment includes a set of 802.11a access points adapted 

to operate as WNs 210a-210d., 211a-211d, and 212a-212d. 

BS 221 further includes Ethernet switch 1210, power supply 

1230, and T1 or other wireline termination (not shown). RF 

router 1220 of BS 221 shown in FIG. 12 is adapted to provide 

RF manager functionality, such as that described above with 

respect to RFMU 220. 

SSs 201a and 201e illustrated in FIG. 12 comprise a mul 

tiple radio access point (e.g., 802.11 “a”, “b', and 'g'), and 

preferably include a router and Ethernet bridge as may be 

built into the access point architecture. Accordingly, such SSS 

may be used as a bridge/router enabling terminal equipment, 

Such as desktop and laptop computers, to be connected to the 

network via Ethernet cable, 802.11b, or 802.11g connections. 

Ofcourse, the use of the 801.11 “a”, “band'g'' protocols can 

be interchanged such that “b’ or 'g' can be used for connec 

tion to the BS while 'a' is used for connection to the terminal 

equipment. It should be appreciated that, according to a pre 

ferred embodiment, the 802.11 access points are used mostly 

for the PHY and the hardware, and the 802.11 MAC is 

replaced to allow the access point to function as described 

above. The foregoing configuration provides for a low cost 

Solution for both the BS and the SS. 

Although the present invention and its advantages have 

been described in detail, it should be understood that various 

changes, Substitutions and alterations can be made herein 

without departing from the invention as defined by the 

appended claims. Moreover, the scope of the present appli 

cation is not intended to be limited to the particular embodi 

ments of the process, machine, manufacture, composition of 

matter, means, methods and steps described in the specifica tion. As one will readily appreciate from the disclosure, pro 

cesses, machines, manufacture, compositions of matter, 

means, methods, or steps, presently existing or later to be 

developed that perform substantially the same function or 

achieve Substantially the same result as the corresponding 

embodiments described herein may be utilized. Accordingly, 

the appended claims are intended to include within their 

Scope such processes, machines, manufacture, compositions 

of matter, means, methods, or steps. 

Case 2:23-cv-00444-JRG Document 1-3 Filed 09/27/23 Page 22 of 23 PageID #: 63
US 7,769,050 B2 

27 

What is claimed is: 

1. A method for providing wireless communication, the 

method comprising: 

providing a plurality of frequency channels in each of a 

plurality of portions of a service area, wherein the plu 

rality of frequency channels are in an unlicensed fre 

quency band, wherein a same frequency channel of the 

plurality of frequency channels is provided for use in 

two or more adjacent portions of the service area; and 

mitigating interference associated with external interfer 

ence Sources by making particular channels of the plu 

rality of channels available for use by network nodes 

disposed in the portions of the service area according to 

a two tier scheduling strategy, 

wherein a first tier of the scheduling strategy includes 

assigning the plurality of frequency channels to each 

portion of the service area at a relatively slow pace; 

wherein a second tier of the scheduling strategy includes 

allocating the assigned frequency channels resulting 

from the first tier of the scheduling strategy among the 

network nodes disposed in each portion of the service 

area in real-time; and 

wherein the network nodes are selected for simultaneous 

use of said particular channels as a function of spatial 

characteristic groupings of said network nodes. 

2. The method of claim 1, wherein the step of mitigating interference comprises: 

Selecting a channel from said plurality of channels for 

communication with a particular network node using adaptive dynamic channel selection to identify a channel 

having a best communication attribute with respect to 

said network node. 

3. The method of claim 1, wherein the step of mitigating interference further comprises: 

Selecting a time division of said particular channels for use 

in communicating with particular network nodes based 

upon dynamically determined communication link met 

rics. 

4. The method of claim 1, wherein the step of mitigating interference comprises: 

Selecting at least two channels from said plurality of chan 

nels for communication with a particular network node 

Such that transmission of identical data on said at least 

two channels is provided for post data selection. 

5. The method of claim 1, wherein the step of mitigating interference comprises: 

Selecting at least two channels from said plurality of chan 

nels for communication with a particular network node 

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35 

40 

45 

28 

Such that data is divided for transmission on said at least 

two channels for time/frequency coding. 

6. The method of claim 1, wherein the step of mitigating interference comprises: 

limiting transmission duty cycles of network nodes with 

respect to each active channel of said plurality of chan 

nels. 

7. The method of claim 3, wherein the dynamically deter 

mined communication link metrics comprise one of interfer 

ence level information, signal propagation level information, 

traffic load information, and quality of service information. 

8. The method of claim 1, wherein said mitigating interfer 

ence comprises assigning a different channel of said plurality 

of channels for use by a particular network node in an uplink 

and a downlink. 

9. A wireless communication network system, comprising: 

a plurality of communication sectors of a service area, 

wherein each communication sector has a plurality of 

network nodes and a plurality of channels associated 

therewith, and wherein adjacent ones of said communi 

cation sectors have at least one same channel of said 

plurality of channels associated therewith; and 

channel management control apparatus making particular 

channels of said plurality of channels available for use 

by the network nodes as a function of external interfer 

ence experienced with respect to one or more channels 

of said plurality of channels, wherein the channel management control apparatus imple 

ments an at least two tier channel Scheduling strategy: wherein a first tier of the channel scheduling strategy 

includes assigning the plurality of channels to each com 

munication sector at a first rate, and where a second tier 

of the channel scheduling strategy includes allocating 

the assigned channels resulting from the first tier of the 

channel scheduling strategy among the network nodes in 

each communication sector in real-time, the first rate 

being less than real-time; 

wherein the first tier of the channel scheduling strategy assigns transmission time period opportunities to com 

munication network base station nodes to Support 

groups of Subscriber station nodes; 

wherein the second tier of the channel Scheduling strategy assigns transmission time periods among Subscribersta 

tion nodes of the groups of subscriber station nodes; and 

wherein the channel management control apparatus makes 

a different channel of the plurality of channels available 

for use by a particular network node in an uplink and a 

downlink. 

Case 2:23-cv-00444-JRG Document 1-3 Filed 09/27/23 Page 23 of 23 PageID #: 64