|Publication number||US5210771 A|
|Application number||US 07/739,037|
|Publication date||11 May 1993|
|Filing date||1 Aug 1991|
|Priority date||1 Aug 1991|
|Also published as||CA2092292A1, CA2092292C, CN1066301C, CN1069610A, DE4292564C2, DE4292564T0, DE4292564T1, WO1993003558A1|
|Publication number||07739037, 739037, US 5210771 A, US 5210771A, US-A-5210771, US5210771 A, US5210771A|
|Inventors||Dennis R. Schaeffer, Michael D. Kotzin|
|Original Assignee||Motorola, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (18), Non-Patent Citations (2), Referenced by (164), Classifications (16), Legal Events (5)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The present invention relates, in general, to spread-spectrum communication systems and, more particularly, to a multiple user spread-spectrum communication system.
The purpose of a communication system is to transmit information-bearing signals from a source (transmitter) to a destination (receiver) using a channel. The transmitter processes (modulates) the message signal into a form suitable for transmission over the channel. The receiver then demodulates the received signal to produce an estimate of the original message signal.
In any communication system, a key parameter which impacts system performance is the transmitter power. In a noise limited communication system, the transmitted power determines the allowable separation between the transmitter and receiver. The available transmitted power determines the signal-to-noise ratio at the receiver input which, for successful communication of information to occur, must exceed some prescribed threshold.
Another key performance criterion for certain communication systems relates to the number of simultaneous users that can be accommodated. An example of one well known system application is a cellular radio telephone system. Such systems are, typically, comprised of a number of base sites, each having a service coverage area, and a number of mobile or hand portable cellular telephones (hereinafter referred to as "subscribers"). The service coverage areas of base sites may be arranged to partially overlap in such a manner as to provide a substantially continuous coverage area in which a subscriber communication unit receiving service from one base site may be handed off to an adjacent remote site with no interruption in service. It is a key goal for a cellular communication system to effectively utilize the available spectrum so that as many users as possible can be accommodated.
Signal multiplexing permits the simultaneous radio transmission of signals from several message sources over a common spectral resource. Frequency division multiplex, time division multiplex, and mixtures thereof have traditionally been used for implementing cellular radio systems.
In a frequency division multiplex (FDM) system, the communication spectral resource is divided into several narrow frequency bands. For at least the time needed to communicate the desired traffic, one frequency division channel is occupied by the subscriber for communicating to the base site. Another frequency channel is used for traffic from the base site to the subscriber.
Time-division multiplex (TDM) systems are another type of multiple access communication system. In a TDMA system, the spectral resource is divided into repeating time frames each having a plurality of time slots or time division channels. Each time division channel is assigned to a different communication link. In this scheme, a portion of a subscriber's information occurs during an assigned slot of a frame. This is followed by one or more other time slots where information to or from other subscribers is accommodated. This process is repeated with received information being appropriately reconstructed at the receiver.
Both analog and digital transmission methods are used to transmit a message signal over a communication channel. Of recent, digital methods have become preferred due to several operational advantages over analog methods, including, inter alia: increased immunity to channel noise and interference; flexible operation of the system; common format for the transmission of different kinds of message signals; improved security of communications through the use of digital encryption; and increased capacity.
To transmit a message signal (either analog or digital) over a band-pass communication channel, the message signal must be manipulated into a form suitable for efficient transmission. Modification of the message signal is achieved by means of modulation and numerous suitable methods are well known in the art. Correspondingly, a receiver is required to recreate the original message.
Spread spectrum communication systems utilizing code division multiple access (CDMA) techniques can be used as multiple access systems like FDMA and TDMA systems. In a spread spectrum system a modulation technique is utilized in which the information is spread over a wide frequency band. The frequency band is much wider than the minimum bandwidth required to transmit the information being sent.
In a direct sequence CDMA system, communication between two communication units is accomplished by spreading each transmitted signal over a wide frequency band with a unique user spreading code. As a result, a multiplicity of transmitted signals share the same frequency. The ability of such a system to work is based on the fact that each signal is specially time and/or frequency coded to facilitate its separation and reconstruction at the receiver. Particular transmitted signals are retrieved from the communication channel by despreading a signal from the sum of signals in the communication channel with a known user spreading code related to the particular spreading accomplished at the transmitter.
In the digital direct sequence system, radio carrier modulation is performed after spreading the user's information with a digital code sequence whose bit rate is much higher than the information rate. A pseudo-random number (PN) is used as a code to "spread" the spectrum. The receiver, by utilizing the same known PN, can properly decode the received signal--even when corrupted with other user's spread signals--and reproduce the original information. The number of simultaneous users that can be accommodated in such a system is dependent on the amount of spectrum "spreading" that is implemented.
Another type of spread spectrum communication is "frequency hopping". In frequency hopping, the frequency of the carrier is shifted using a pattern dictated by a code sequence. The transmitter jumps from one frequency to another within some predetermined set. At the receiver, the hopping sequence for the desired user is known and allows tracking of the user's hopping transmissions. Periodically, more than one user's signal will fall on the same frequency thereby causing interference. Information coding techniques (error correction coding) are used to enable reconstruction of the original information even when a fraction of the transmitted bursts are lost. There are also time hopping and time-frequency hopping schemes whose times transmission are regulated by the code sequence.
Any of the multiple access systems can be utilized cellular radio communication systems. In cellular systems, several factors limit performance. Typically, in propagating through the channel, a transmitted signal is distorted because of nonlinearities and imperfections in the frequency response of the channel. Other sources of degradation are noise (thermal and man made) and adjacent and co-channel interference.
Besides the typical sources of degradation mentioned above, the majority of the noise associated with a received signal in a spread spectrum CDMA system comes from the other user's signals which are transmitted in the same frequency band but with unique user spreading codes. A noise power contribution to the desired despread signal exists for each of the other individual user's signals. The magnitude of the added noise is directly related to the received signal power of each of the undesired signals. An undesired received signal that comes in much stronger than the desired signal contributes excess noise. Therefore, it is desirable to dynamically adjust the power of all users in such a way that they are received with approximately the same power. In this manner, the number of users that can be simultaneously accommodated with the same spectrum resource is maximized.
In typical applications, to accomplish the needed power control, it would be necessary for the closest transmitters to reduce their power by as much as 80 dB when compared to the power of the furthest transmitters. This range in power control is extremely difficult to achieve and highly cost prohibitive.
Therefore, a means is needed by which communication using a spread spectrum format may be optimized without the requirement of an 80 dB power range.
The present invention comprises a multiple user spread-spectrum communication system having a site employing a plurality of communication channels. Each channel is assigned a desired received signal strength threshold. Subscriber units are assigned to appropriate channels based upon their received signal strength in a manner to permit their operation within their limited power control range. The subscriber units achieve this threshold by dynamically adjusting their transmit power.
In a particular embodiment, after a signal has been initially received from a subscriber unit and the power measured, the system selects a channel having an assigned received signal strength threshold for the subscriber signal that is compatible with the subscriber's dynamic power control range. The subscriber unit is instructed to transmit on the selected channel. Once assigned to a particular channel, the output power of the subscriber's transmitter is adjusted to match the received signal strength threshold assigned to that channel.
In another particular embodiment, the communication channel comprises non-overlapping time division channels of one or more radio frequency carriers.
In yet another particular embodiment of the present invention, the above communication system may be applied using channels employing a combination of frequency and non-overlapping time divisions, each being assigned to different power levels.
FIG. 1 is a graph representing a prior art FDMA communication scheme;
FIG. 2 is a graph representing a prior art spread spectrum communication scheme;
FIG. 3 is an abstract representation of a reconstructed communication signal from the prior art spread spectrum communication scheme;
FIG. 4 is a graphical representation of a cell site;
FIG. 5 is a graph representing a spread spectrum communication scheme illustrating the present invention;
FIG. 6 is a graphical representation of a cell site using the spread spectrum scheme of FIG. 5;
FIG. 7 is a graph representing another spread spectrum communication scheme illustrating the present invention;
FIG. 8 is a graph representing still another spread spectrum communication scheme illustrating the present invention; and
FIG. 9 is a graph representing one method for assigning received signal strength thresholds in a spread spectrum communications.
Referring initially to the graph, generally designated 10, of FIG. 1, a prior art FDMA communication scheme is illustrated. In FIG. 1, the abscissa is assigned the frequency values and the ordinate is assigned the amplitude value. A plurality of signals 12 are illustrated on graph 10. Ideally, each signal would be in a distinct frequency range 11. A transmitter/receiver pair would be tuned to frequency range 11 and only receive the signal within that range.
In FIG. 2, a graph, generally designated 20, representing a prior art spread spectrum communication scheme is illustrated. In a spread spectrum system, communication between two units is accomplished by spreading each signal over the frequency band of the channel. Each signal is spread with a unique user spreading code. This is illustrated in graph 20 by taking the energy of each of the separate signals and distributing it over the entire channel The height of 12' is indicative of the received power level In the abstract illustration of FIG. 3, one of the signals has been reconstructed. As shown, because the other signals are distributed over the same frequency range as the reconstructed signal, there is some interference (represented by the cross-hatched area). However, the spread spectrum scheme is designed such that a reconstructed signal 12 will exceed the noise from other signals by enough that the quality of signal 12 will not be degraded.
In order to maximize the number of users for the spread spectrum scheme, it is desirable to have each of the signals at the same power level from the stand point of the receiver (cell site). An example of a cell site, generally designated 40 within a cellular system, is provided in FIG. 4. Site 40 consists of a boundary 41, a base site 42, and users 43a and 43b. As shown, the distance from user 43a to base site 42 is greater than the distance from user 43b to base site 42. Therefore, if both users were operating at the same power level, the signals received at base site 42 may be much greater for user 43b because of its closer proximity.
As stated previously, in order to maximize the number of users for the spread spectrum scheme, it is desirable to have signals of equal power received at base site 42. Since the weakest signal will generally be the signal furthest from base site 42, all other signals would be brought down to user 43a's power level.
In one method of operation, base site 42 sends out a control signal to the communication unit of user 43b. This control signal directs user 43b's unit to reduce its power. The problem here is that, in the extreme, user 43b may have to reduce the power of its unit by as much as 80 dB. This degree of power reduction is very difficult to achieve and cost prohibitive in the design of the subscriber communication unit.
In order to address this problem and reduce the power variance (adjustability) needed, the present invention is provided as a solution. In essence, the present invention will divide the communication spectrum into two or more channels; with each channel being assigned to a signal based upon the signal's power. A graphical example of this is provided in a graph of a spread spectrum scheme (e.g. CDMA), generally designated 50, in FIG. 5. The channel of FIG. 2 has now been divided into three channels S1-S3. Each channel has a plurality of signals having approximately the same amount of power within each segment. In this example, channel S1 has the highest power signals, then channel S3. Channel S2 contains the signals having the lowest power level.
Placing this in practice can be illustrated in the cell site, generally designated 60, of FIG. 6. Here, cell 60 is shown with secondary boundary lines 41a and 41b. It should be noted here that this example is based upon the assumption that the signals from units closer to base 42 are stronger than those from units further away. Since propagation anomalies and units having different power output levels will occur, this is not always necessarily the case in practice.
Comparing the scheme of FIG. 5 with the cell site of FIG. 6, units transmitting within the area inside boundary 41b would be placed in the S1 channel, since these would be the strongest signals. Signals from units between the 41a and 41b boundary lines would be placed in channel S3; and signals from units outside the 41a boundary would be placed in channel S2. Therefore, user 43b's signal would be placed in channel S1 and user 43a's signal would be placed in channel S2.
In using this scheme, the user's power output can be centered in it's dynamic power control range. As the unit traverses the cell's coverage area, the user's power output may reach it's power control upper limit. If the received power level dropped below this level, the user would be shifted to a channel having a lower received signal strength threshold. Likewise, a user's power may reach it's power control lower limit. In this situation the unit would be shifted to a channel having a higher received signal strength threshold. As a result, rather than requiring a power range in the 80-90 dB range, a range of 20-30 dB would be sufficient.
As explained above, the preceding discussion was under the assumption that closer units provide higher power signals as opposed to those units further away. In actual practice, the power levels need not be based upon a geographic breakdown, as shown in FIG. 6, but could be based upon the power of the received signal. For example, the signal from user 43a may be powerful enough that the system would place this signal in area S3. Alternatively, the signal from user 43b may be very weak (e.g. because it is in a building or obstructed by an obstacle) causing the system to place that signal in channel S2.
There are several methods for determining the appropriate channel for a particular user. In one method, which has been described above, the cell site--based on measured received power level from the user--would select a channel having a received signal strength threshold level within the subscriber's power control range. In another method, the cell site will transmit received signal strength threshold information for each channel available at the base site and the current power level setting for the base control channel. The subscriber's unit would then measure the control channel received power level and calculate the power loss. A channel having a receive power level that will place the subscriber's unit transmit power within its dynamic range would then be selected. The choice of method used depends on the state of the current subscriber. The first method is most appropriate for placing the unit within it's power control range within the cell when established communications are in progress or when the unit is handed off to another cell in a system. The second method is more appropriate for the initial access of the subscriber to the system at the start of a communication session.
Once the initial channel assignment has been made, the transmit power of the subscriber unit can be adjusted as needed to keep the signal received at the site at or near the appropriate received signal strength threshold. If, for example, the subscriber is moving closer to the site and is unable to reduce its transmit power by enough to maintain the appropriate received signal strength, then the signal can be moved from one channel to another having a higher received signal strength threshold.
In the practical implementation of the spread spectrum communication system of FIG. 5, it is highly desirable to set the thresholds for adjacent channels such that they do not differ drastically from each other. It will be apparent to those experienced in the art that having different thresholds imposes additional requirements of limiting sideband energy from modulated signals in adjacent channels; and improved filtering requirements in receivers to protect signals on the desired channel from adjacent channel signals that are at higher received power levels. FIG. 9 depicts one method of arranging the thresholds to reduce interference from stronger adjacent channel signals. Since it is generally unknown what interference can be expected from services in adjacent frequency bands, organizing according to FIG. 9 (e.g. establishing high power threshold levels for channels s1 and s9 which are next to the system band edges) will make these channels less susceptible to the interference. The more vulnerable channels s4-s6 which have the lowest power level thresholds are centered in the system where adjacent channel interference is controlled by the system.
Referring now to FIG. 7, a graph, generally designated 70, representing another spread spectrum communication scheme illustrating the present invention is provided. In graph 70, a spread spectrum scheme such as described in conjunction with FIG. 5 is applied in a TDMA fashion to one spread spectrum channel. In graph 70, the ordinate value is now time as opposed to frequency. Here, a particular frequency has been divided into time slots T1 -T3, 71-73 respectively. Each time slot is a time division channel and is assigned a particular power level. When a communication signal is received at the base station, depending upon the power of the received signal, it is assigned to a particular time division channel, 71-73. Again, the signal may be controlled by the base station to increase/decrease power to more appropriately match the power level of the time division channel in which it is being placed.
In FIG. 8, a graph, generally designated 80, representing yet another spread spectrum communication scheme illustrating the present invention, is provided. Graph 80 is a three dimensional graph having time added as the third dimension. Graph 80 represents a combination of the schemes of FIGS. 5 and 7. Here, the communication channel has been divided into frequency bandwidth segments S1-S3. Each frequency bandwidth segment has then been divided into time slots T11 -T33. By assigning a different power level to each segment/slot combination, the communication system can assign incoming signals to segment/slot locations which more closely match the incoming signal's power level.
Therefore, it will be clear to one skilled in the art that the instant invention allows the dynamic power control range necessary for a spread spectrum communication system to be greatly reduced. This in-turn permits the use of simpler and less expensive transceiver designs while still maximizing system capacity.
Thus, it will be apparent to one skilled in the art that there has been provided in accordance with the invention, a process and method that fully satisfy the objects, aims, and advantages set forth above.
While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alterations, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alterations, modifications, and variations in the appended claims.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US3706933 *||17 Sep 1963||19 Dec 1972||Sylvania Electric Prod||Synchronizing systems in the presence of noise|
|US4532636 *||18 Jun 1982||30 Jul 1985||The Marconi Company Limited||Radio communications receivers|
|US4638479 *||6 Dec 1984||20 Jan 1987||U.S. Philips Corporation||Method of two-way radiocommunication between fixed stations and mobile stations|
|US4653069 *||6 Nov 1975||24 Mar 1987||General Electric Company||Spread spectrum correlation receiver|
|US4665404 *||19 Oct 1984||12 May 1987||Offshore Navigation, Inc.||High frequency spread spectrum positioning system and method therefor|
|US4817089 *||27 Mar 1987||28 Mar 1989||International Mobile Machines Corporation||Subscriber RF telephone system for providing multiple speech and/or data signals simultaneously over either a single or a plurality of RF channels|
|US4821120 *||12 Jun 1986||11 Apr 1989||Devon County Council||Television sub-carrier transmission|
|US4866710 *||22 Feb 1988||12 Sep 1989||Motorola, Inc.||Reuse groups for scan monitoring in digital cellular systems|
|US4943974 *||21 Oct 1988||24 Jul 1990||Geostar Corporation||Detection of burst signal transmissions|
|US4972506 *||17 Feb 1989||20 Nov 1990||Telefonaktiebolaget L M Ericssson||Method of transmitting data information in a mobile, cellular radio communication system|
|US5029183 *||29 Jun 1989||2 Jul 1991||Symbol Technologies, Inc.||Packet data communication network|
|US5067136 *||12 Jul 1990||19 Nov 1991||Axonn Corporation||Wireless alarm system|
|US5093840 *||16 Nov 1990||3 Mar 1992||Scs Mobilecom, Inc.||Adaptive power control for a spread spectrum transmitter|
|US5101501 *||7 Nov 1989||31 Mar 1992||Qualcomm Incorporated||Method and system for providing a soft handoff in communications in a cdma cellular telephone system|
|US5103460 *||12 Sep 1990||7 Apr 1992||Clarence H. Stewart||Spread spectrum intercept apparatus and method|
|US5109390 *||7 Nov 1989||28 Apr 1992||Qualcomm Incorporated||Diversity receiver in a cdma cellular telephone system|
|US5128959 *||22 Feb 1991||7 Jul 1992||Motorola, Inc.||Variable bandwidth CDMA radio system|
|US5131006 *||24 Dec 1990||14 Jul 1992||Ncr Corporation||Carrier detection for a wireless local area network|
|1||Fred Baumgartner, "Code Division Multiple Access Beyond the Time Domain", Communications Feb. 1990; pp. 26-32.|
|2||*||Fred Baumgartner, Code Division Multiple Access Beyond the Time Domain , Communications Feb. 1990; pp. 26 32.|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US5317593 *||3 Mar 1993||31 May 1994||Motorola, Inc.||Communication device with code sequence and frequency selection system|
|US5335246 *||15 Oct 1992||2 Aug 1994||Nexus Telecommunication Systems, Ltd.||Pager with reverse paging facility|
|US5335249 *||29 Jul 1993||2 Aug 1994||Seattle Silicon Corporation||Method and apparatus for spread spectrum communications|
|US5381443 *||2 Oct 1992||10 Jan 1995||Motorola Inc.||Method and apparatus for frequency hopping a signalling channel in a communication system|
|US5430759 *||24 Nov 1993||4 Jul 1995||Nexus 1994 Limited||Low-power frequency-hopped spread spectrum reverse paging system|
|US5499266 *||22 Dec 1994||12 Mar 1996||Nexus 1994 Limited||Low-power frequency-hopped spread spectrum acknowledgement paging system|
|US5506863 *||25 Aug 1993||9 Apr 1996||Motorola, Inc.||Method and apparatus for operating with a hopping control channel in a communication system|
|US5519718 *||22 Dec 1994||21 May 1996||Nexus 1994 Limited||Remote unit for use with remote pager|
|US5530452 *||22 Dec 1994||25 Jun 1996||Nexus Telecommunication Systems Ltd.||Method of synchronizing spread spectrum radio transmitters|
|US5579306 *||1 Sep 1994||26 Nov 1996||Ericsson Inc.||Time and frequency slot allocation system and method|
|US5581547 *||3 Mar 1994||3 Dec 1996||Ntt Mobile Communications Network Inc.||Random access communication method by CDMA and mobile station equipment using the same|
|US5608724 *||27 Sep 1995||4 Mar 1997||Nippondenso Co., Ltd.||Dynamically reconfigurable frequency division multiplexer and modulator|
|US5610940||7 Jun 1995||11 Mar 1997||Omnipoint Corporation||Method and apparatus for noncoherent reception and correlation of a continous phase modulated signal|
|US5627856||7 Jun 1995||6 May 1997||Omnipoint Corporation||Method and apparatus for receiving and despreading a continuous phase-modulated spread spectrum signal using self-synchronizing correlators|
|US5629956||7 Jun 1995||13 May 1997||Omnipoint Corporation||Method and apparatus for reception and noncoherent serial correlation of a continuous phase modulated signal|
|US5648955||7 Jun 1995||15 Jul 1997||Omnipoint Corporation||Method for power control in a TDMA spread spectrum communication system|
|US5648982||9 Sep 1994||15 Jul 1997||Omnipoint Corporation||Spread spectrum transmitter|
|US5659303 *||20 Apr 1995||19 Aug 1997||Schlumberger Industries, Inc.||Method and apparatus for transmitting monitor data|
|US5659574||7 Jun 1995||19 Aug 1997||Omnipoint Corporation||Multi-bit correlation of continuous phase modulated signals|
|US5668828 *||23 Sep 1994||16 Sep 1997||Sanconix, Inc.||Enhanced frequency agile radio|
|US5670964 *||1 Feb 1995||23 Sep 1997||Ericsson Inc.||Navigation assistance for call handling in mobile telephone systems|
|US5671219||7 Jun 1995||23 Sep 1997||Omnipoint Corporation||Communication protocol for spread spectrum communication|
|US5680414||7 Jun 1995||21 Oct 1997||Omnipoint Corporation||Synchronization apparatus and method for spread spectrum receiver|
|US5689502 *||5 Jun 1995||18 Nov 1997||Omnipoint Corporation||Efficient frequency division duplex communication system with interleaved format and timing adjustment control|
|US5692007||7 Jun 1995||25 Nov 1997||Omnipoint Corporation||Method and apparatus for differential phase encoding and decoding in spread-spectrum communication systems with continuous-phase modulation|
|US5694414||7 Jun 1995||2 Dec 1997||Omnipoint Corporation||Multi-band, multi-mode spread-spectrum communication system|
|US5742593 *||29 Aug 1995||21 Apr 1998||Hazeltine Corporation||On-line distributed TDMA/FDMA/CDMA link assignment in mobile radio networks with flexible directivity|
|US5745484 *||5 Jun 1995||28 Apr 1998||Omnipoint Corporation||Efficient communication system using time division multiplexing and timing adjustment control|
|US5754584||7 Jun 1995||19 May 1998||Omnipoint Corporation||Non-coherent spread-spectrum continuous-phase modulation communication system|
|US5754585||7 Jun 1995||19 May 1998||Omnipoint Corporation||Method and apparatus for serial noncoherent correlation of a spread spectrum signal|
|US5757847||7 Jun 1995||26 May 1998||Omnipoint Corporation||Method and apparatus for decoding a phase encoded signal|
|US5768264||7 Jun 1995||16 Jun 1998||Omnipoint Corporation||Time division multiple access base station supporting ISDN messages|
|US5787076||18 Feb 1997||28 Jul 1998||Omnipoint Corporation||Multi-mode TDMA spread spectrum communication system|
|US5790587||7 Jun 1995||4 Aug 1998||Omnipoint Corporation||Multi-band, multi-mode spread-spectrum communication system|
|US5793757 *||13 Feb 1996||11 Aug 1998||Telefonaktiebolaget L M Ericsson (Publ)||Telecommunication network having time orthogonal wideband and narrowband sytems|
|US5796772||7 Jun 1995||18 Aug 1998||Omnipoint Corporation||Multi-band, multi-mode spread-spectrum communication system|
|US5802046 *||5 Jun 1995||1 Sep 1998||Omnipoint Corporation||Efficient time division duplex communication system with interleaved format and timing adjustment control|
|US5815525||27 Mar 1996||29 Sep 1998||Omnipoint Corporation||Multi-band, multi-mode spread-spectrum communication system|
|US5818820||7 Jun 1995||6 Oct 1998||Omnipoint Corporation||Method and system for data link expansion or contraction using spread spectrum TDMA communication|
|US5825757 *||11 Jan 1996||20 Oct 1998||Nokia Mobile Phones Limited||Methods and apparatus for excluding communication channels in a radio telephone|
|US5832028||7 Jun 1995||3 Nov 1998||Omnipoint Corporation||Method and apparatus for coherent serial correlation of a spread spectrum signal|
|US5841808 *||23 Mar 1995||24 Nov 1998||Mcdonnell Douglas Corporation||Spread spectrum chip rate tracking system|
|US5856998||18 Dec 1996||5 Jan 1999||Omnipoint Corporation||Method and apparatus for correlating a continuous phase modulated spread spectrum signal|
|US5859842 *||8 Nov 1995||12 Jan 1999||Omnipoint Corporation||Antenna diversity techniques|
|US5881100||14 Nov 1997||9 Mar 1999||Omnipoint Corporation||Method and apparatus for coherent correlation of a spread spectrum signal|
|US5887020||18 Aug 1994||23 Mar 1999||Omnipoint Corporation||Multi-band, multi-mode spread-spectrum communication system|
|US5898230 *||6 Nov 1997||27 Apr 1999||Kiekert Ag||Motor vehicle with a central locking unit and a remote control for its operation|
|US5917812 *||16 Apr 1996||29 Jun 1999||Qualcomm Incorporated||System and method for reducing interference generated by a digital communication device|
|US5937002 *||13 Jul 1995||10 Aug 1999||Telefonaktiebolaget Lm Ericsson||Channel hopping in a radio communication system|
|US5953370||12 Sep 1997||14 Sep 1999||Omnipoint Corporation||Apparatus for receiving and correlating a spread spectrum signal|
|US5959980 *||5 Jun 1995||28 Sep 1999||Omnipoint Corporation||Timing adjustment control for efficient time division duplex communication|
|US5963586||7 Jun 1995||5 Oct 1999||Omnipoint Corporation||Method and apparatus for parallel noncoherent correlation of a spread spectrum signal|
|US5991625 *||7 Aug 1996||23 Nov 1999||Omnipoint Corporation||Spread spectrum wireless telephone system|
|US6005856 *||21 Jun 1996||21 Dec 1999||Omnipoint Corporation||Communication protocol for spread spectrum wireless communication system|
|US6018528 *||28 Apr 1994||25 Jan 2000||At&T Corp||System and method for optimizing spectral efficiency using time-frequency-code slicing|
|US6035197 *||29 Dec 1994||7 Mar 2000||Cellco Partnership||Method and system for providing a handoff from a CDMA cellular telephone system|
|US6041046 *||14 Jul 1995||21 Mar 2000||Omnipoint Corporation||Cyclic time hopping in time division multiple access communication system|
|US6064662 *||14 Sep 1998||16 May 2000||At&T Corp||System and method for optimizing spectral efficiency using time-frequency-code slicing|
|US6064883 *||9 Jul 1998||16 May 2000||Trw Inc.||Method and apparatus for autonomous user terminal assignment of time and frequency slots for call handoff|
|US6088590||1 Aug 1994||11 Jul 2000||Omnipoint Corporation||Method and system for mobile controlled handoff and link maintenance in spread spectrum communication|
|US6094421 *||21 Jan 1997||25 Jul 2000||Omnipoint Corporation||Timing adjustment control for efficient time division duplex, frequency division duplex or hybrid time division duplex/frequency division duplex communication|
|US6094575||4 Mar 1996||25 Jul 2000||Omnipoint Corporation||Communication system and method|
|US6112080||31 Dec 1996||29 Aug 2000||Omnipoint Corporation||Wireless communication method and system|
|US6144648 *||23 Oct 1997||7 Nov 2000||Nec Corporation||Communication system for making carrier synchronous|
|US6161013||26 Jul 1996||12 Dec 2000||Omnipoint Corporation||Wireless communication system and method|
|US6195362||8 Nov 1996||27 Feb 2001||At&T Corporation||Resource pooling system and method in communication systems|
|US6229792||7 Jun 1995||8 May 2001||Xircom, Inc.||Spread spectrum communication system|
|US6240292||23 Nov 1999||29 May 2001||Cellco Partnership||Method and system for providing a handoff from a CDMA cellular telephone system|
|US6246713||8 Jun 1998||12 Jun 2001||Telefonaktiebolaget Lm Ericsson (Publ)||Frequency-hopping in a bandwidth-on-demand system|
|US6259685 *||3 Sep 1999||10 Jul 2001||Nokia Telecommunications Oy||Method for channel allocation utilizing power restrictions|
|US6259686 *||29 Jul 1998||10 Jul 2001||France Telecom||Multiple access method in a cellular radio communication network|
|US6282228 *||20 Mar 1997||28 Aug 2001||Xircom, Inc.||Spread spectrum codes for use in communication|
|US6317452||7 May 1999||13 Nov 2001||Xircom, Inc.||Method and apparatus for wireless spread spectrum communication with preamble sounding gap|
|US6324209||12 May 2000||27 Nov 2001||Golden Bridge Technology Inc.||Multi-channel spread spectrum system|
|US6366566||8 Jul 1999||2 Apr 2002||Xircom Wireless, Inc.||Efficient communication system using time division multiplexing and timing adjustment control|
|US6388997||25 Apr 2000||14 May 2002||Xircom Wireless, Inc.||Timing adjustment control for efficient time division duplex communication|
|US6396817 *||31 Aug 1998||28 May 2002||Qualcomm Incorporated||Signal splitting method for limiting peak power in a CDMA system|
|US6522642||2 Jul 1998||18 Feb 2003||Intel Corporation||Antenna diversity techniques|
|US6532365||29 Aug 2000||11 Mar 2003||Intel Corporation||PCS pocket phone/microcell communication over-air protocol|
|US6577611||27 May 1998||10 Jun 2003||Nokia Mobile Phones Limited||Methods and apparatus for excluding communication channels in a radio telephone|
|US6577612 *||25 Nov 1998||10 Jun 2003||Siemens Aktiengesellschaft||Transmission system for transmitting digital signals on a radio subscriber line network|
|US6611692||4 Sep 2002||26 Aug 2003||At&T Wireless Services, Inc.||Cordless cellular system|
|US6681118||25 Oct 2002||20 Jan 2004||At&T Wireless Services, Inc.||Method of providing cellular and landline cordless service using a dual mode mobile telephone|
|US6704546 *||6 Apr 1999||9 Mar 2004||Nortel Matra Cellular||Method and apparatus for allocation of a transmission frequency within a given frequency spectrum|
|US6732163||5 Jan 2000||4 May 2004||Cisco Technology, Inc.||System for selecting the operating frequency of a communication device in a wireless network|
|US6735432||4 Nov 1998||11 May 2004||At&T Wireless Services, Inc.||Cordless cellular system and method|
|US6751187||26 Jun 2001||15 Jun 2004||Qualcomm Incorporated||Method and apparatus for processing data for transmission in a multi-channel communication system using selective channel transmission|
|US6754190 *||17 Oct 2001||22 Jun 2004||Motorola, Inc.||Channel selection method used in a communication system|
|US6810030||17 Oct 1997||26 Oct 2004||Lucent Technology||Dynamic and smart spreading for wideband CDMA|
|US6970518||11 Mar 2003||29 Nov 2005||Motorola, Inc.||Method and apparatus for electronic item identification in a communication system using known source parameters|
|US6993065||5 Oct 2001||31 Jan 2006||Golden Bridge Technology Inc.||Multi-channel spread spectrum system|
|US7023817||11 Mar 2003||4 Apr 2006||Motorola, Inc.||Method and apparatus for source device synchronization in a communication system|
|US7035646||22 Aug 2003||25 Apr 2006||Cingular Wireless Ii, Llc||Cordless cellular system|
|US7072380 *||21 Dec 2000||4 Jul 2006||Interdigital Technology Corporation||Apparatus for initial power control for spread-spectrum communications|
|US7072413 *||14 Jun 2001||4 Jul 2006||Qualcomm, Incorporated||Method and apparatus for processing data for transmission in a multi-channel communication system using selective channel inversion|
|US7218641||11 Mar 2003||15 May 2007||Motorola, Inc.||Method and apparatus for adaptive processing gain for multiple source devices in a communications system|
|US7260620||17 Mar 2004||21 Aug 2007||Cisco Technology, Inc.||System for selecting the operating frequency of a communication device in a wireless network|
|US7457268 *||10 Nov 2004||25 Nov 2008||Alcatel||Scheme for packet allocation in a radiocommunication system|
|US7502406||27 Feb 2002||10 Mar 2009||Interdigital Technology Corporation||Automatic power control system for a code division multiple access (CDMA) communications system|
|US7535874||12 Nov 2004||19 May 2009||Interdigital Technology Corporation||Method and apparatus for adaptive power control for spread-spectrum communications|
|US7548752||22 Dec 2004||16 Jun 2009||Qualcomm Incorporated||Feedback to support restrictive reuse|
|US7596461||6 Jul 2007||29 Sep 2009||Cisco Technology, Inc.||Measurement of air quality in wireless networks|
|US7634536||15 Dec 2009||Cisco Technology, Inc.||System for selecting the operating frequency of a communication device in a wireless network|
|US7649954||30 Jun 2006||19 Jan 2010||Qualcomm Incorporated||Method and apparatus for processing data for transmission in a multi-channel communication system using selective channel inversion|
|US7680475||7 Jun 2005||16 Mar 2010||Qualcomm Incorporated||Dynamic ASBR scheduler|
|US7688899||17 May 2001||30 Mar 2010||Qualcomm Incorporated||Method and apparatus for processing data for transmission in a multi-channel communication system using selective channel inversion|
|US7706332||14 Jul 2005||27 Apr 2010||Interdigital Technology Corporation||Method and subscriber unit for performing power control|
|US7756190||8 Oct 2003||13 Jul 2010||Interdigital Technology Corporation||Transferring voice and non-voice data|
|US7903613||28 May 2004||8 Mar 2011||Interdigital Technology Corporation||Code division multiple access (CDMA) communication system|
|US7929498||19 Apr 2011||Interdigital Technology Corporation||Adaptive forward power control and adaptive reverse power control for spread-spectrum communications|
|US7965688||21 Jun 2011||Qualcomm Incorporated||Signal splitting method for limiting peak power in a CDMA system|
|US8032145||4 Oct 2011||Qualcomm Incorporated||Restrictive reuse set management algorithm for equal grade of service on FL transmission|
|US8040965||9 Jul 2009||18 Oct 2011||Qualcomm, Incorporated|
|US8059589||8 Jun 2005||15 Nov 2011||Qualcomm Incorporated||Dynamic restrictive reuse scheduler|
|US8072896 *||6 Dec 2011||Telefonaktiebolaget L M Ericsson (Publ)||Adaptive coexistence between different wireless communication systems|
|US8233460||23 Jul 2007||31 Jul 2012||Gpne Corp.||Communication system with map of information provided from controller to enable communication with nodes|
|US8305971||13 Jan 2009||6 Nov 2012||Cisco Technology, Inc.||Utilizing persistent interference information for radio channel selection|
|US8311020||13 Nov 2012||GPNE Corporation||Communication system allowing network nodes to efficiently establish communications with a controller|
|US8335195||18 Dec 2012||GPNE Corporation||Communication system allowing node identification|
|US8477858||25 Feb 2010||2 Jul 2013||Qualcomm Incorporated|
|US8483691||18 Jun 2008||9 Jul 2013||Qualcomm Incorporated||Restrictive reuse for a wireless communication system|
|US8488706||14 Sep 2009||16 Jul 2013||Qualcomm Incorporated|
|US8526963||18 Jun 2004||3 Sep 2013||Qualcomm Incorporated||Restrictive reuse for a wireless communication system|
|US8675509||3 Jun 2009||18 Mar 2014||Qualcomm Incorporated||Feedback to support restrictive reuse|
|US8737363||7 Mar 2011||27 May 2014||Interdigital Technology Corporation||Code division multiple access (CDMA) communication system|
|US20020015437 *||5 Oct 2001||7 Feb 2002||Golden Bridge Technology Inc.||Multi-channel spread spectrum system|
|US20020126770 *||9 Mar 2001||12 Sep 2002||Behrouz Pourseyed||Method and system for acquiring narrowband channel information over a wideband channel receiver|
|US20020141478 *||21 Dec 2000||3 Oct 2002||Ozluturk Fatih M.||Apparatus for initial power control for spread-spectrum communications|
|US20030072252 *||17 Oct 2001||17 Apr 2003||Gurney David P.||Channel selection method used in a communication system|
|US20030112880 *||14 Jun 2001||19 Jun 2003||Walton Jay R.|
|US20030193914 *||10 Jan 2001||16 Oct 2003||Gary Lomp||Rapid acquisition spreading codes for spread-spectrum communications|
|US20040009693 *||10 Jul 2003||15 Jan 2004||Tribotek, Inc.||Multiple-contact cable connector assemblies|
|US20040152482 *||22 Aug 2003||5 Aug 2004||At & T Wireless Services, Inc.||Cordless cellular system|
|US20040179510 *||11 Mar 2003||16 Sep 2004||Stephen Kuffner||Method and apparatus for source device synchronization in a communication system|
|US20040179547 *||11 Mar 2003||16 Sep 2004||Stephen Kuffner||Method and apparatus for adaptive processing gain for multiple source devices in a communications system|
|US20040179588 *||11 Mar 2003||16 Sep 2004||Stephen Kuffner||Method and apparatus for electronic item identification in a communication system using known source parameters|
|US20050096061 *||1 Jun 2004||5 May 2005||Qualcomm Incorporated||Layered reuse for a wireless communication system|
|US20050096062 *||18 Jun 2004||5 May 2005||Ji Tingfang||Restrictive reuse for a wireless communication system|
|US20050135414 *||10 Nov 2004||23 Jun 2005||Alcatel||Scheme for packet allocation in a radiocommunication system|
|US20060002360 *||8 Jun 2005||5 Jan 2006||Ji Tingfang||Dynamic restrictive reuse scheduler|
|US20060135169 *||22 Dec 2004||22 Jun 2006||Qualcomm Incorporated||Feedback to support restrictive reuse|
|US20080013494 *||26 Jun 2007||17 Jan 2008||Qualcomm Incorporated||Signal splitting method for limiting peak power in a cdma system|
|US20080014953 *||23 Jul 2007||17 Jan 2008||Gpne Corp.||Communication system with a request by a single node made over one of two separate slots in a frame|
|US20080016229 *||27 Jun 2007||17 Jan 2008||Nhn Corporation||Method and system of running viral advertisement service|
|US20090012738 *||6 Jul 2007||8 Jan 2009||Cisco Technology, Inc.||Measurement of Air Quality in Wireless Networks|
|US20090262785 *||19 Jun 2008||22 Oct 2009||Leif Wilhelmsson||Adaptive Coexistence Between Different Wireless Communication Systems|
|US20100002597 *||7 Jan 2010||Qualcomm Incorporated||Feedback to support restrictive reuse|
|US20100074351 *||25 Mar 2010||Qualcomm Incorporated|
|US20100104039 *||14 Sep 2009||29 Apr 2010||Qualcomm Incorporated|
|US20100177710 *||13 Jan 2009||15 Jul 2010||Igal Gutkin||Utilizing persistent interference information for radio channel selection|
|US20100246704 *||30 Sep 2010||Qualcomm Incorporated|
|US20110026499 *||3 Feb 2011||Gpne Corp.||Communication system with a mapping system allowing nodes to register with a controller|
|US20110170677 *||14 Jul 2011||Gpne Corp.||Communication system allowing network nodes to efficiently establish communications with a controller|
|EP0910181A2 *||13 Oct 1998||21 Apr 1999||Lucent Technologies Inc.||Dynamic and smart spreading for wideband CDMA|
|EP1322128A1 *||24 Aug 2001||25 Jun 2003||Sanyo Electric Co., Ltd.||Radio receiving system and method|
|EP2482577A1 *||22 Oct 2004||1 Aug 2012||Qualcomm Incorporated(1/3)||Layered Reuse for a Wireless Communication System|
|WO1994021064A1 *||17 Feb 1994||15 Sep 1994||Motorola Inc.||Device with code sequence and frequency selection|
|WO1995007587A1 *||8 Sep 1994||16 Mar 1995||Ericsson Ge Mobile Communications, Inc.||Navigation assistance for call handling in mobile telephone systems|
|WO1996002979A2 *||13 Jul 1995||1 Feb 1996||Telefonaktiebolaget Lm Ericsson||Channel hopping in a radio communications system|
|WO1996002979A3 *||13 Jul 1995||7 Mar 1996||Knut Magnus Almgren||Channel hopping in a radio communications system|
|WO1996010300A1 *||22 Sep 1995||4 Apr 1996||Sanderford Hugh Britton Jr||Enhanced frequency agile radio|
|WO1998025362A1 *||27 Oct 1997||11 Jun 1998||Motorola Inc.||Method and system for optimizing a traffic channel in a wireless communications system|
|WO2003001702A1 *||25 Jun 2002||3 Jan 2003||Qualcomm Incorporated||Method and apparatus for processing data for transmission in a multi-channel communication system using selective channel transmission|
|WO2005046283A1 *||22 Oct 2004||19 May 2005||Qualcomm Incorporated||Layered reuse for a wireless communication system|
|U.S. Classification||375/132, 370/330, 370/335, 375/140, 375/138|
|International Classification||H04B7/005, H04J4/00, H04B7/26, H04W36/16, H04W52/50|
|Cooperative Classification||H04J4/00, H04W36/16, H04W52/50|
|European Classification||H04J4/00, H04W36/16, H04W52/50|
|1 Aug 1991||AS||Assignment|
Owner name: MOTOROLA, INC., ILLINOIS
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNORS:SCHAEFFER, DENNIS R.;KOTZIN, MICHAEL D.;REEL/FRAME:005796/0611
Effective date: 19910725
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|16 Apr 2015||AS||Assignment|
Owner name: GOOGLE TECHNOLOGY HOLDINGS LLC, CALIFORNIA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:MOTOROLA MOBILITY LLC;REEL/FRAME:035441/0001
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