WI-LAN Inc. v. Alcatel-Lucent USA Inc. et al

Filing 182

REPLY to 167 Claim Construction Brief,,,,, filed by WI-LAN Inc.. (Attachments: # 1 Affidavit Declaration of Jeffrey T. Han, # 2 Exhibit I - true and correct copy of U.S. Patent No. 5,603,095, # 3 Exhibit II - true and correct copy of U.S. Patent No. 5,239,682, # 4 Exhibit III - true and correct copy of U.S. Patent No. 5,659,598., # 5 Exhibit IV - true and correct copy of WO 96/37054., # 6 Exhibit V - true and correct copy of Sanford Bingham, Multiplexers, Computerworld, Nov. 27, 1989, at 61., # 7 Exhibit VI - true and correct copy of David J. Stang, Network)(Weaver, David)

Download PDF
EXHIBIT II 111111111111111111111111111111111111111111111111111111111111111111111111111 United States Patent USOO5239682A [19] [11] Strawcynski et al. [54] [75] [45] INTER·CELL CALL HAND·OVER IN RADIO COMMUNICATION SYSTEMS WITH DYNAMIC CHANNEL ALLOCATION Inventors: Leo Strawcynski; Howard M. Sandler, both of Ottawa; Gregory L. Plett, North Gower; Dand G. Steer, Nepean, all of Canada [73] Assignee: [21] Appl. No.: 710,867 [22] Filed: [30] Northern Telecom Limited, Montreal, Canada Jun. 6, 1991 Foreign Application Priority Data Dec. 5, 1990 [CAl Canada ................................. 2031551 [51] [52] Int. Cl.l ......................... A04B 7/00; H04B 17/00 U.S. Cl................................... 455/54.1; 455/56.1; [58] 455/62; 379/59 Field of Search .................... 455/33.1,33.2, 33.4, 455/54.1,54.2,56.1,62; 379/58, 59, 60 [56] References Cited U.S. PATENT DOCUMENTS 5,239,682 Aug. 24, 1993 5,093,926 3/1992 Sasufa ................................... 455/62 Primary Examiner-Reinhard J. Eisenzopf Assistant Examiner-Lisa Charouel Attorney, Agent, or Firm-Jean·Pierre Fortin [57] ABSTRACI' The call hand-over technique of this invention is characterized by the use of channel information from both the target base station and subscriber terminal in determining which radio traffic channel will be used to hand over a call in progress from a serving base station to a target base station. Calls are handed over to the radio channel which, of a set of channels under consideration by the subscriber terminal, contains the least amount of interference as measured by the subscriber terminal. The set of channels under consideration by the subscriber terminal is a subset of the entire set of channels allocated to the service. This subset is comprised of those channels having little interference, as measured by the target base station. The hand-over technique thereby assures that calls proceed on channels containing little interference from the viewpoints of both the target base station and subscriber terminal. 4,475,010 10/1984 Huensch et al. ................... 455156.1 5,038,399 8/1991 Bruckert ............................... 455/62 SERVING BASE STATION SUBSCRIBER TERMINAL Patent Number: Date of Patent: 7 Claims, 6 Drawing Sheets TARGET BASE STATION SEL A GP. OF CANDIDATE TRAFFIC CH. WITH LOW r----I WITH LOW INTERFR. SEND GROUP OF TRAFF I C CH. TO SUB. TER. SEND GROUP OF TRAFF I C CH. TO SERVING BASE STATION SEND CANDIDATE TRAFFIC CH. T o r - - - - - , TARGET ASE STATION WIL-0192815 u.s. Patent Aug. 24, 1993 Sheet 1 of 6 5,239,682 r------------, wi Ql u. u. o x CD CL L ___________ ~J .- .- WIL-0192816 u.s. Patent Sheet 2 of 6 Aug. 24, 1993 5,239,682 .C\I C\I • C) iI: )C m a. C\I .C\I :. WIL-0192817 u.s. Patent Aug. 24, 1993 I 5,239,682 Sheet 3 of 6 • I £Xl ::,) en 0 IW en «( £Xl ~ T L.IJ (f) « '(f) 0 .... - NlD (W) - -LL Cl (f) 0 .... - NlD ID 0 t- c:: UJ ID a: u C')(f) ::c U L.IJ UJ ~ (f)(f) ~t: \.OlD "!:teo 1 T c:: (f) 01- - NID (f) 01- - NlD L.IJ c:: (f) lD ::::> (f) 0 .... C\I L.IJ z z «( ::c u LLJ LLJ ::J: "!:t "!:t c.. (.) I C (f)(f) ~t: \.OlD (f) C "'\.:"3 '. h ., w eo u L 0 en - .... NID ns In -.:r C Z c( £Xl Z ~ WIL-0192818 u.s. Patent Aug. 24, 1993 SUBSCRIBER TERMINAL SERVING BASE STATION Sheet 4 of 6 5,239,682 TARGET - BASE ST ATION SEl. A GP. OF CANDIDATE TRAFFIC CH. WITH LOW INTERFR SCAN EACH CANDIDATE TRAFFIC CH. IN GP. SEND GROUP OF SEND GROUP OF TRAFFIC CH. TO TRAFFIC CH. TO 14------1 SUB. TER ...-~ SERVING BASE STATION SELECT & SEND A SEND CANDIDATE CANDIDATE TRAFFIC CH. t---~TRAFFIC CH. TO WITH LOW TARGET INTERFR. BASE STATION FIG.4a WIL-0192819 u.s. Patent Aug. 24, 1993 SUBSCRIBER TERMINAL * r--__ Sheet 5 of 6 SERVING BASE ST ATION 5,239,682 TARGET BASE STATION ONITOR CHANNEL FOR INTERFERENCE SEND RECEIVE RECEIVE REQUEST REQUEST REQUEST FOR NEW ~---4~ FOR NEW t------t~ FOR NEW CHANNEL CHANNEL CHANNEL DO INTER-CELL CALL HANDOVER TO CANDIDATE TRAFF I C CH ANNEL DO INTER-CELL CALL HANDOVER TO CANDIDATE TRAFFIC CHANNEL DO INTER-CELL CALL HANDOVER TO CANDIDATE TRAFFIC CHANNEL FIG.4b WIL-0192820 u.s. Patent Aug. 24, 1993 SUBSCRIBER TERMINAL Sheet 6 of 6 SERVING BASE STATION .... ...--- 5,239,682 TARGET BASE STATION MONITOR CHANNEL FOR INTERFERENCE YES RECEIVE REQUEST FROM SERVING STATION SEND RECEIVE REQUEST REQUEST I-----~ FROM FOR NEW SERVING CHANNEL ST ATION DO INTER-CELL CALL HAND-O VER TO CANDIDATE TRAFFIC CHANNEL DO INTER-CELL CALL HANO-O VER TO CANDIDATE TRAFFIC CHANNEL DO INTER-CELL CALL HAND-OVER TO CANDIDATE TRAFFIC CHANNEL FIG.4c WIL-0192821 1 5,239,682 2 As indicated above, when this is done without changing INTER-CELL CALL HAND-OVER IN RADIO the base station that communicates with the subscriber, COMMUNICATION SYSTEMS WITH DYNAMIC it is known as an "intra-ceU" hand-over, i.e., within a CHANNEL ALLOCATION cell. 5 When either an intra- or inter-cell hand-over is perFIELD OF THE INVENTION formed in a DCA system, a suitable radio channel must be selected to continue the call. In present systems inThis invention relates to radio communication systems which use dynamic channel allocation, especially, corporating DCA, the determination of which channel but not restricted to, cellular radio systems. is used for a call set-up or hand-over is made according 10 to channel information from the base station or the DESCRIPTION OF THE PRIOR ART subscriber terminal. The disadvantage with this apA duplex radio link conveying user analogue and/or proach is that appreciable interference may be present on the selected channel from the viewpoint of the other digital information shall henceforth be referred to as a "call". An example is a telephone call over a wireless end of the link. For example, a traffic channel may have 15 little appreciable interference, as monitored by the servchanne1. Cellular radio communication systems are able to ing base station. However, the same traffic channel may have unacceptable interference at the subscriber termiservice a high volume of traffic with a limited amount of radio spectrum by re-using the same radio channels in na1 or at the target base station if a inter-cell handover is attempted. Therefore, the presence of interference sufficiently separated cells. In conventional city-wide mobile cellular systems, such as the North American 20 Advanced Mobile Phone System, the frequency allocamay reduce the quality of the link and also make it more susceptible to any further channel impairments which tions for a specific cell are fixed; Le., each cell can make might arise. . use of only a specified subset of channels of those allocated to the entire service. The allocations of channels Accordingly, it is an object of the present invention require careful engineering analyses of radio propaga- 25 to provide an improved method of performing inter-cell tion conditions and traffic patterns within and between hand-over in radio systems with DCA, characterized by the cells. Fixed allocation cellular radio systems are the use of channel information from both the target base engineered so that harmful levels of interference from station and subscriber terminal in determining which signals used in neighbouring cells are unlikely to be traffic channel to use. 30 encountered. SUMMARY OF THE INVENTION When the communication link is changed without The hand-over procedures of this invention require changing the base station that communicates with the that there be a means of communicating call supervisubscriber, it is known as an "intra-cell" hand-over, i.e., sory information between a base station and a subscriber within a cell. A description of an intra-cell handover is disclosed in a co-pending application entitled "Im- 35 terminal. A suitable means is an in-band signalling chanproved Intra-cell Call Handover in Radio Communicanel associated with each traffic channel. When a subtion Systems with Dynamic Channel Allocation" filed scriber moves away from a serving cell towards or into on Jun. 6, 1991 and having Ser. No. 07/710,866. On the an adjacent cell, or moves within range of another base other hand, when a subscriber terminal moves out of the station, an inter-cell handover maybe necessary. In adcoverage area of one base station and into that of an- 40 vance of an inter-cell hand-over, the target, i.e., proother, the call may be maintained by switching the spective new base station, compiles a list of candidate communication link to the closer base station. This is traffic channels which have low interference from its known as an "inter-cell" hand-over, i.e., between cells. perspective (and are not otherwise undesirable due to Micro-cellular radio systems tend to use dynamic, additional information known to the base stati~m). This rather than fixed, channel allocation. With dynamic 45 list is passed via a wired link to the original base station. channel allocation (DCA) each cell can potentially use The original base station conveys the information over any traffic channel for a given call of those allocated to the inband or associated signalling channel to the subthe entire service. The decision as to which channel to scriber terminal. The subscriber terminal checks these use is made dynamically. i.e. based on channel usage candidates, chooses the traffic channel which has the conditions experienced at the time of call set-up. The 50 lowest interference from its perspective, and reports decision is also made in a decentralized manner, i.e. by this choice to the original base station over the associthe base station or subscriber terminal in question, withated signalling channel. The original base station conout any centralized coordination with other cells. This veys this information to the target base station via the has the advantages that no detailed engineering analyses are required for each cell site, cell sites can easily be 55 wired link. If an inter-cell hand-over becomes necessary, the call proceeds on the agreed-upon traffic chanadded or moved, and more traffic can be handled than nel to the target base station. with fixed allocation, because channels unused in neighAccordingly, an aspect of the present invention is to bouring cells can be "borrowed". Examples of radio provide a method of performing a radio channel handsystems which use DCA are the digital U.K. CT2 system, and some models of analogue North American 60 over in a radio system with dynamic channel allocation, from a serving base station in communication with a 46/49 MHz cordless telephones. subscriber terminal to a target base station, comprising A disadvantage of DCA, however, is that interferthe steps of: ence may suddenly arise in an existing call if another selecting, from a plurality of traffic channels, a numcall is set up on the same or an adjacent channel in a nearby cell. Without fixed channel assignments, free- 65 ber of suitable traffic channels, as measured at the target base station; dom from interference is not assured. To escape from forwarding, from the target base station to the servinterference, an existing call may need to be handed over to a radio channel which is free from interference. ing base station, a message indicative of which traffic WIL-0192822 3 5,239,682 4 channels were determined suitable at the target base station 24b, the call is handed over from the serving base station 240 to the target base station 24b. station; sending the message to the subscriber terminal along Referring now to FIGS. 2 and 40, the base station a signalling channel linking the serving base station and 24b, which has been selected to be the target base staS tion, would scan all available traffic channels, and select the subscriber terminal; traffic channels that are useable or free of interference receiving the message at the subscriber terminal; at the base station's end of the link. It is to be noted that selecting, from the traffic channels indicated by the the base stations could also be configured such that all message, a traffic channel that is also suitable at the traffic channels are prescanned. That is, the base stasubscriber terminal; forwarding, to the serving base station, a response 10 tions could scan the traffic channels continuously or on a regular interval and thereby maintain a list of useable message indicative of a selected traffic channel; traffic channels. A list of frequencies or traffic channels sending the response message to the target base station; and is made and forwarded to serving base station 240 via an switching to the selected radio channel at the subinter base station link or trunk. 26a and 26b linking the scriber terminal and the target base station. 15 serving base station 240, the target base station 24b and PBX 20. In the preferred embodiment, only a certain BRIEF DESCRIPTION OF THE DRAWINGS number of traffic channels would be selected as useable. FIG. 1 is an illustration of a typical low power radio For example, the base station could be configured to system embodying the invention; select the first 3 traffic channels with interference levels FIG. 2 illustrates how a call hand over can be imple- 20 below a threshold. Similarly, the base station could also mented in a low power radio system such as shown in be configured to select the 3 traffic channels which FIG. 1; have the lowest interference levels. If there are no suffiFIG. 3 illustrates the frame structure ofa traffic chancient traffic channels with interference below the nel; and threshold, then, additional channels with interference FIGS. 40 to 4c are flow diagrams illustrating the 25 levels above the threshold may be selected as well. The inter-cell hand-over technique of the present invention. traffic channels selected would be those that have the lowest interference levels even though the levels are DESCRIPTION OF THE PREFERRED above the threshold. It will of course be understood that EMBODIMENT if some of the latter traffic channels are considered to In the illustration of FIG. 1, a low-power wireless 30 otTer inadequate communication between the base stacommunication system is shown. A typical network can tion and the subscriber terminal, they would be exeluded from the selection. The serving base station 240 consist of one or more small base stations, such as shown at reference numeral 11. In FIG. 1, base station then forwards the list of traffic channels to the sub11 is connected to the Public Switched Telephone Netscriber terminal 22 via the inband or associated signalwork (PSTN) 12. Base stations are basically used as 35 ling channel. Once received, the list of useable frequenradio transceivers. These can be deployed in offices, cies or traffic channels, is scanned by subscriber termiresidences, and public areas, such as airports, gas stanal 22. The subscriber terminal can then select frequentions and shopping malls, etc. Base stations form the cies or traffic channels of those indicated in the list interface between a number of subscriber terminals such which are also free of interference at the subscriber end as portable handsets 13a and 13b and PSTN 12. Simi- 40 of the link. In the preferred embodiment, the traffic larly, several base stations, such as those shown at referchannel determined to contain the least interference ence numerals 140 and 14b can also be linked to a host, level of those scanned is selected by the subscriber tersuch as a private branch exchange PBX 15 to provide minal. coverage of larger areas, in say, a private business or Once the traffic channel containing the least interferoffice building. A subscriber terminal 16 could there- 45 ence is selected, the subscriber terminal sends a message fore operate in an office building via base station 140 or to the serving base station 240 on the inband or associ14b and outside thereof, via base station 11. Such a ated signalling channel providing an indication of wireless PBX system is disclosed in U.S. Pat. No. which traffic channel was selected. The serving base 4,771,448. station then forwards the selection to the target base Referring now to FlO. 2, we have shown a low 50 station 24b. As shown in FIGS. 4b and 4c, if an inter-cell power wireless communication system which can be hand-over becomes necessary, the subscriber terminal installed in a private business or office building. A PBX 22 and the target base station 24b are switched over to 20 is used by POTS (Plain Old Telephone Service) 21 the selected channel and the call continues. If none of and a wireless subscriber terminal 22 to establish call the traffic channels in the list were determined to be connections to PSTN 23. Base stations 240 and 24b can 55 adequate, a message can be sent to the base station indibe placed at various locations in the office building to eating that the call hand-over between the subscriber allow the use of a wireless subscriber terminal 22 where terminal and the target base station cannot proceed. required. In the illustration, subscriber terminal 22 is The hand-over Can then be initiated, by instructing being served by base station 240. In the event that interboth the target base station and the subscriber terminal ference arises on the communication channel linking the 60 to switch to the selected channel. The serving base base station and the subscriber terminal, an intracell station would then release the channel once the handhandover may be necessary. That is, another channel over is complete. without interference would be selected. A description The signalling and traffic channels of the wireless of an intra-cell handover is disclosed in a co-pending communication system may be used in time-division application entitled "Improved Intra-cell Call Hand- 65 duplex mode. That is, base station and subscriber termiover in Radio Communication Systems with Dynamic nal alternately transmit so that their transmissions do Channel Allocation". In the event that the subscriber not overlap. This technique is commonly referred to as terminal moves to an area which is better served by base "pingpong". This is shown in FIG. 3. WIL-0192823 5 5,239,682 6 2, A method as derIDed in claim 1, wherein said group As is shown, the frame structure is comprised of one of candidate traffic channels are selected at the target slot 42 used for communication between the base station base station by: and the subscriber terminal and another slot 43 for comscanning each traffic channel in said plurality of trafmunication between the subscriber terminal and the fic channels; detecting the interference level on the scanned traffic base station, Each slot contains a voice or data portion 44 and an inband or associated signalling channel comchannels,and selecting the scanned traffic channel as the candidate prised of two sets of bits 45a and 4Sb, In the preferred embodiment, the voice or data portion contains 64 bits traffic channel if the interference level is below a of information per frame and the inband or associated Hi first predetermined threshold, 3, A method as defIDed in claim 2, wherein additional signalling channel contain four bits of information per frame, candidate traffic channels are selected from the plurality of traffic channels available for service if an inadeWhat is claimed is: I, A method of performing a radio channel hand-over quate number of the candidate traffic channels were in a radio system with dynamic channel allocation, from 15 found to have interference levels below the fIrSt predetermined threshold, 4, A method as defined in claim 5, wherein if addia serving base station in communication with a subscriber terminal to a target base station, comprising the tional candidate traffic channels are selected, a traffic steps of: channel of the additional candidate traffic channels selecting, at said target base station, from a plurality 20 having the lowest mterference level above the fIrst of traffic channels, a group of candidate traffic predetermined threshold will be selected, 5, A method as defIDed in claim 4, wherein if any channels, with low interference levels as measured at the target base station; remaining traffic channels in said plurality have an exforwarding, from the target base station to the servcessive level of interference offering inadequate coming base station, a message indicative of the candi- 25 munication between the target base station and the subdate traffic channels in said group; scriber terminal, they will be excluded from the selec' 'b ' tion, A 6 thod d fi d' l' 2 h ' 'd sen dIDg th e message f rom t h e servmg ase station to 'be ' I al '11' h I ' me as e me m c 81m , W erem sat mest,he ,subscn r t~rmIDa on~ a signa IDg c ~ne sage is sent to the serving base station by: grouping as a list, each candidate traffic channel idenlmking the servmg base station and the subscnber 30 terminal; tifled as having low interference levels at the target receiving the message at the subscriber terminal; base station; and scanning each candidate traffic channel in said group forwarding to the serving base station the list of the indicated by the message; candidate traffic channels, along an inter base staselecting, the candidate traffic channel from said 35 tion connection link, , group having a lowest interference level, as mea7, A method as defIned ~ c1,aim 6, w~erein the candisured at the subscriber terminal' date traffic channel on the Itst IS detemuned to have low , " , interference levels at the subscriber terminal by: forwardmg,' to the servIDg base statIOn, , a response ' eac 'd 'fi , , scanrungh cand'date tramIC ch anne1 I ent! Ied on I message mdlcattve of the selected candIdate traffic 40 the list, channel; detecting'the interference level on each scanned cansending the response message to the target base stadidate traffic channel' and tion; and selecting the candidate traffic channel with the lowswitching to the selected candidate traffic channel at est interference level. • • • • • the subscriber terminal and the target base station, 45 50 55 60 65 WIL-0192824

Disclaimer: Justia Dockets & Filings provides public litigation records from the federal appellate and district courts. These filings and docket sheets should not be considered findings of fact or liability, nor do they necessarily reflect the view of Justia.

Why Is My Information Online?