Showing papers on "Base station published in 1993"

Signal and interference statistics of a CDMA system with feedback power control. II

Abstract: For pt.I see ibid., vol 41, p.1626-34 (1993). Power control is essential in the use of direct-sequence code division multiple-access (CDMA) techniques. Early system-level performance analyses of a CDMA approach to wireless mobile and personal communications have assumed the ability of power control to equalize the absolute signal powers of CDMA users received at each base station. The present paper studies a more practical, although analytically more complicated, uplink power control technique that uses measurements of the received signal-to-interference ratio (SIR) instead. A combination of discrete-event link simulation and analysis of the obtained SIR statistics is used to explore the previously little-known behavior of a CDMA system using SIR-based power control and to obtain performance estimates for such a system under various operating assumptions. The overall results indicate that power control based on SIR has the potential for somewhat higher system performance than power control based on absolute signal strength assumed in the early analyses. >

Performance of power-controlled wideband terrestrial digital communication

Abstract: Performance of a wideband multipath-fading terrestrial digital coded communication system is treated. The analysis has applications to a cellular system using direct-sequence spread-spectrum code-division multiaccess (CDMA) with M-ary orthogonal modulation on the many-to-one reverse (user-to-base station) link. For these links, power control of each multiple-access user by the cell base station is a critically important feature. This feature is implemented by measuring the power received at the base station for each user and sending a command to either raise or lower reverse link transmitter power by a fixed amount. Assuming perfect interleaving, the effect of the power control accuracy on the system performance is assessed. >

Method of wireless communication between base station and mobile station and multiple access communication system

Abstract: In a communication system having a base station for controlling a transmission right and a plurality of substations, a substation having data to be transmitted transmits the number of necessary fragments and its address to a request field of a communication frame. The base station uses a plurality pair of fragment slots and reply slots following the request field in the communication frame to transmit an address of a substation permitted to transmit data, to each fragment slot. The substation permitted to transmit data transmits the address of a destination substation and the data to a predetermined field following the address in one fragment slot. The destination station transmits a reply signal indicating the reception state of the data to the reply slot paired with the fragment slot. If the base station detects from the reply signal that the destination station failed in receiving the data, the base station instead of the substation first transmitted the data transmits the destination address and data received at the fragment slot to the next fragment slot.

Apparatus and method for reducing message collision between mobile stations simultaneously accessing a base station in a CDMA cellular communications system

Abstract: Collisions between messages simultaneously transmitted by multiple spread-spectrum transmitters are reduced by distributing the transmissions over the available resources of the receiver. The transmitters may be mobile stations and the receiver may be a base station in a CDMA cellular telephone system. Each mobile station uses one or more randomization methods to distribute its transmissions. In the first randomization, the mobile station time- delays its transmissions by a number of chips of the PN code with which it spreads the transmitted signal. A hash function produces the number from an identification number uniquely associated with that mobile station. In a second randomization, the mobile station randomly selects the PN code. In a third randomization, the mobile station inserts a random delay between successive message transmissions or probes if it does not receive an acknowledgement after a predetermined timeout period. A predetermined number of such transmissions is called a probe sequence. In a fourth randomization, the mobile station inserts a relatively long random delay between successive probe sequences if it does not receive an acknowledgement of any probe in the sequence. The noise level is reduced by minimizing transmission power. The mobile station increments the power of successive probes within each probe sequence. The first probe of each probe sequence is transmitted at a predetermined level.

Wireless direct sequence spread spectrum digital cellular telephone system

Abstract: The base station (10) serves up to 62 handsets (11-1, 11-2, ..., 11-N) and has a single antenna (13); however, polarization diversity is provided in each of the handsets (11-1, 11-2, ..., 11-N) by using dual cross polarized antennae (11A1 and 11A2). The base station (10) includes an up/down converter and distribution amplifiers (14); a transceiver (12) for each handset (11-1, 11-2, ..., 11-N); a common reference oscillator (15); a telephone system interface (17); and clock logic circuitry (16).

Wireless digital personal communications system having voice/data/image two-way calling and intercell hand-off

Abstract: A wireless digital personal communications system (or PCS) having a plurality of radio cell base stations, fixed terminals, and portable handset terminals, each having a predetermined radio cell coverage area. The wireless PCS has a full digital network interface. The personal communications system facilitates the interconnection and switching of PCS call traffic through the digital network interface and the public switched telephone network, or any switched network. The personal communications system has voice/data/image (or any combination thereof) and incoming and outgoing calling capability. The PCS is fully operational and compatible with any and all modulation approaches selected for wireless communications. The intercell protocol hand-off being provided through distributed logic which is implemented in software that is resident in the intelligent portable handset terminals, in the intelligent fixed terminals, in the intelligent base stations, and in the public switched telephone network (or any switched network). Alternative embodiments of the present invention include a wireless digital personal communications system having authentication means for authenticating a remote device; a wireless digital personal communications system having a combination of authentication means for authenticating a remote device and security means for securing signal and message content between an intelligent base station and a remote device, the security means including a predetermined encryption and decryption technique; a wireless digital personal communications system having dynamic zone grouping of portable handset terminals or fixed terminals; and a wireless digital personal communications system having call forwarding for unanswered calls.

Tracking mobile users in wireless communications networks

Abstract: Tracking strategies for mobile wireless networks are studied. A cellular architecture in which base stations that are interconnected by a wired network communicate with mobile units via wireless links is assumed. The cost of utilizing the wireless links for the actual tracking of mobile users is considered. A tracking strategy in which a subset of all base stations is selected and designed as reporting centers is proposed. Mobile users transmit update messages only upon entering cells of reporting centers, while every search for a mobile user is restricted to the vicinity of the reporting center to which the user last reported. It is shown that, for an arbitrary topology of the cellular network (represented by the mobility graph), finding an optimal set of reporting centers is an NP-complete problem. Optimal and near-optimal solutions for important special cases of the mobility graph are presented. >

Radio coverage in closed environments

Abstract: A repeater system in a communication system including a base station and a mobile unit provides a communications link between the base station and the mobile unit when the mobile unit is located in an environment that is substantially closed off to high radio frequency communication between the base station and the mobile unit. The repeater system has a first linear two-way frequency converter including a high frequency port for two-way coupling to the base station and a low frequency port for two-way coupling to a low frequency signal that is capable of distributing radio frequency power through the closed environment. The low frequency port is connected to a cable which propagates and receives low radio frequency power within the closed environment. The repeater system also includes a first antenna for wireless coupling to the cable, and a second linear two-way frequency converter having a low frequency port connected to the first antenna for two-way coupling to a low frequency signal and a high frequency port for two-way coupling to a signal that is compatible with the high radio frequency signal used by the communications system. A second antenna is connected to the high frequency port of the second linear two-way frequency converter for wireless coupling of the second linear two-way frequency converter to a nearby mobile unit.

Segregation method of dynamic channel allocation in a mobile radio system

Abstract: A method for adaptively allocating channels for connections between base station and mobiles is disclosed. The channels accessible to the base stations for establishing connections with mobiles are ranked in at least one priority list based on transmission loss intervals. Each channel is ranked in the priority list according to their success at previous connections. The amount of power required for a channel allocated from a list associated with a low transmission loss can be set lower thereby reducing the interference associated with the channel and increasing system capacity. A self planned system evolves where channels are allocated for connections based on their past connection history. Thus, the selection of channels which may interfere with calls in neighboring cells or which may suffer substantial interference from a neighboring base is avoided.

Wireless communications using near field coupling

Abstract: Near field coupling is employed for transferring data back and forth between base stations and portable stations in cellular communication systems, such as cellular local area networks

Method and apparatus for coordinating transfer of information between a base station and a plurality of radios

Abstract: To efficiently coordinate the transmission of information from a plurality of radios to a base station on the forward channel of an RF channel, transmission time on the forward channel is scheduled by the base. To be allowed to transmit information on the forward channel, a radio first sends a request frame to the base to request permission to access the forward channel. After sending the request frame, the radio waits for the base to assign it a reserved information time slot. Only if an information time slot is reserved, and only during that reserved time slot, may the radio send an information frame on the forward channel. In determining whether to reserve an information time slot for the radio, the base station takes into consideration the priority of the radio. This allows the base station to better coordinate signal activity on the forward channel. Since transmission time on the forward channel is scheduled, conflicting transmissions are minimized. Thus, forward channel capacity is used more efficiently.

Cellular communications test system

Abstract: A testing system (28) for wireless communication networks, particularly cellular networks, having a test set (30, 36) located in a cell site which communicates through the cell's base station to a responder (32, 38) at the mobile telephone switching office (MTSO, 34). The test set (30, 36), which includes a measurement module (48), controller (44), modem (46), and cellular phone (50), initiates the call to the responder (32, 38), and directs the responder to transmit and receive certain test signals which are then measured by the measurement module. The test set (30, 36), which may be fixed or mobile, provides essentially continuous monitoring of voice channels within a given cell, and can send an alarm in near real-time to the network control center when a faulty voice channel is detected.

Low-power wireless system for telephone services

Abstract: A small telephone system provides telecommunications services for personal wireless telephone sets over an area which is divided into service cells. Each of the cells is defined by reception characteristics of a plurality of radio base stations within the cell. During a call progress, if the wireless telephone set is mobile, a radio link with the set is handed off from one cell to another as the wireless telephone set moves along. The telephone system includes a service controller and a port being wireline connected between each radio base station and the service controller. The service controller selects radio base stations for setting up radio links with wireless sets of a calling or called persons, and responds to received signal strengths for handing a radio link from radio base station to radio base station, to maintain the quality of the radio link with an active mobile wireless telephone set.

Frequency hopping spread spectrum data communications system

Abstract: A frequency hopping spread spectrum wireless data communications network is disclosed. Time mark frames are transmitted by each base station at a regular cadence and each time mark frame contains all information necessary to determine the hopping sequence of channels, a sub-set of possible channels in use, and the particular channel upon which the time mark was transmitted. Receipt of the time mark resynchronizes a slot clock that is used by the wireless terminals in implementing a media access protocol with defined synchronous time slots. The base station to roaming terminal radio link is half duplex. Each base station broadcasts an end-of-message frame during a hop period that indicates that it has no more data to send during that hop. If there are no inbound messages a roaming terminal needs to send, it puts its receiver in a low power mode until the next hop time approaches. Look ahead acquisition of the hopping sequence for a nearby base station when the received signal level for the current base station drops is also disclosed.

Method of carrying out an authentication check between a base station and a mobile station in a mobile radio system

Abstract: Methods for carrying out an authentication check in a mobile telephone system in which an authentic base station serves a plurality of mobile stations. A prior method carried out a unidirectional check from the base to a calling mobile, permitting a false base to carry out a false authentication check by collecting a number of so-called RAND-Response pairs. To avoid this problem, another unidirectional, base-to-mobile, authentication check and an authentication check from the mobile to the base are carried out. In one embodiment, only the bi-directional authentication check is carried out.

Method and apparatus for providing mixed voice and data communication in a time division multiple access radio communication system

Abstract: A system is described which integrates terminal traffic in a digital voice cellular radio communication system. Data is conveyed from remote data stations and remote radio telephone stations over a reverse channel TDMA frame. The allocation of time slots in the reverse channel TDMA frame is controlled at the base station. The base station provides priority to radio telephones having digitized voice traffic. The base station assigns time slots within the reverse channel TDMA frame based upon allocation requests received from radio telephone stations and remote data stations. Remote data stations may contend on a random access for a minority of a set of time slots in the reverse channel data frame. Additionally, they may request an assigned slot by inserting an allocation request in a control slot of the reverse channel data frame. The base station allocates time slots on a voice radio telephone priority, and assigns any excess time slots to data stations waiting for access to the reverse channel.

Unified approach to prediction of propagation over buildings for all ranges of base station antenna height

Abstract: Theoretical results for the dependence on base station antenna height of the average received signal for mobiles at street level are presented. The results apply to residential and commercial sections of cities and to all ranges of antenna height from well above to below that of the surrounding buildings. Assuming all buildings to be of equal heights, the range dependence of the average signal is found by evaluating multiple forward diffraction past rows of buildings. The solution for this diffraction problem for sources near to or below the rooftops gives the dependence of the range index on antenna height and base station height gain, which are in agreement with measurements. These results will be of importance for proposed systems for personal communication services, which envision the use of base station antennas at the height of lamp posts, as well as cellular mobile radio. >

Tracking mobile users in wireless communications networks

Abstract: Tracking strategies for mobile wireless networks are studied, assuming a cellular architecture where base stations interconnected by a wired network communicate with mobile units via wireless links The cost of utilizing the wireless links for the actual tracking of mobile users is investigated A tracking strategy in which a subset of all base stations is selected and designated as reporting centers is proposed Mobile users transmit update messages only upon entering cells of reporting centers, while every search for a mobile user is restricted to the vicinity of the reporting center to which the user last reported It is shown that for an arbitrary topology of the cellular network (represented by the interference graph), finding an optimal set of reporting centers is an NP-complete problem Optimal and near-optimal solutions for important special cases of the interference graph are given >

Packet data transfer in a cellular radio system

Abstract: The invention relates to packet data transfer in a digital cellular radio system comprising at least one common organization channel for sending pages, connection requests, and channel assignments so as to establish an actual connection on another channel. In the invention the user data is transferred from the mobile stations (MS) to the base station (BTS1-BTS4) interleaved with the connection request messages on at least one random-access-type organization channel in messages which will not result in a normal connection establishment. The mobile station sends a random-access-type packet data transfer request on the random-access-type organization channel. A timing advance corresponding to the distance between the base station and the mobile station is determined on the basis of the request received at the base station. The mobile station then utilizes the timing advance for sending data packets on the random-access-type organization channel in messages longer than said transfer request by timing the transfer of the messages with respect to the operation of the base station.

Interactive nationwide data service communication system for stationary and mobile battery operated subscriber units

Abstract: In a two-way interactive communication video network having a network switching center (2) for point-to-point communications between subscribers at different geographic locations, a local base station (3) configuration is provided for facilitating low power battery operated portable subscriber units (17). The local subscriber units surrounding a base station are adapted for multiplex transmission of digital messages synchronously related to a broadcast television signal for system coordination. Digital messages are transmitted from the local subscriber units to the base station data processing facility through a set of receive only cell site subdivision zones distributed over the base station transmitter geographical range, which communicate with the base station data processing facility over a communication link such as wired cable. Messages are compiled and relayed by satellite to a network switching center transmitter site for nationwide point-to-point communications. Small-size, inexpensive, low-power, portable, digital-transmitting subscriber units are introduced compatible with interactive video data system standards with the ability to cross subdivision and cell zones. Thus, monitoring of inventory, temperature, and other parameters for passive automatic alarm systems and the like, as well as active mobility of subscriber units for meter reading and the like is made possible with direct low-cost nationwide real time reporting capability.

Zone registration of a mobile in a mobile telephone system

Abstract: In a service area of a mobile telephone system, there are plural base radio stations. A mobile radio station in the service area broadcasts a request signal of zone registration. All the base stations in the service area receive this request signal, measure the field intensity of the signal, and transmit the value of the measured intensity to the mobile radio station. The mobile radio station transmits a response signal to a base radio station where the field intensity is the highest. This response signal is reported to a radio channel control unit where the contents of the zone register is revised in accordance with the reported response.

Power control method for use in a communication system

Abstract: The power of a received signal is measured at a base station. This measured power is used to predict a future power level of the received signal and from that to determine the appropriate power adjustment command. The power adjustment command is then sent to the transceiver.

Procedure for the handover of a radio connection

Abstract: In a digital micro or pico cell network based on Time Division Multiple Access, comprising a Mobile Services Switching Center, Base Station Controllers with which a number of Base Transceiver Stations have been connected, and several Mobile Stations, a handover can be accomplished so that the parameters required in identifying a Mobile Station, and the frequency data, the data of the time interval to be used, as well as the frame number data of the channel are given to a new Base Transceiver Station to which a Mobile Station will be moved The new Base Transceiver Station is tuned to listen to the channel determined by the data it received The former Base Station transmits a handover command to the Mobile Station containing the frequency data, the data of the time interval to be used, as well as the frame number data of the channel to which the new Base Station has moved After the command the Mobile Station turns the trafficing directly to said channel The timing measurements between the Base Station and the Mobile Station are not carried out

Method and apparatus providing handoff of a mobile station between base stations using parallel communication links established with different time slots

Abstract: The soft handover of a channel or a base station according to the invention functions especially well in a TDMA system with a high TDMA milo. For the time of preparation of handover parallel physical links are formed between the mobile station (MS) and two or more base stations (BTS1, BTS2), whereby these base stations transmit the same signal to the mobile station (MS) in different time slots, and possibly in a different frequency.

Tdma for mobile access in a cdma system

Abstract: A method and system for increasing the capacity of radiotelephone communication systems by eliminating interference to communication traffic caused by random access burst from unconnected mobile station are disclosed. Access slots are provided in CDMA signals by interrupting other communication traffic of mobile stations using the same frequency at periodic intervals. This allows mobile access bursts to be received at a base station without interfering with other traffic.

Capacity improvement of base-station antenna arrays cellular CDMA

Abstract: In this paper, the use of antenna arrays at base-station for cellular CDMA is discussed. We present a performance analysis for a multiple cell CDMA cellular system with an antenna array at base-station for both base-station to mobile (downlink) and mobile to base station (uplink) links. Considering the effects of path loss, Rayleigh fading, log-normal shadowing, multiple access interference, and the thermal noise, we show that using an antenna array at base-station, both in receiving and transmitting, to resolve angular positions of the mobiles, leads to a many-fold increase in system capacity. We also present simulation results. >

Mobile assisted handover using cdma

Abstract: A mobile station assists the wireless network with handover from a first base station to a second base station. The mobile station receives transmissions from the first base station using a first spreading code corresponding to the first base station while receiving signals from at least one other base station. The mobile station determines the relative signal strengths of the signals received from the other base stations and reports the relative signal strengths to the first base station to support handover determinations by the wireless network.

A method of effecting random access in a mobile radio system

Abstract: A method for random access in a time divided mobile radio system, for instance an FDMA/TDMA system, which includes digital traffic channels and control channels which are organized so that four traffic channels (TC) and two control channels (CC) are included in a TDMA-frame. A base station (BS) transmits continuously flags (B/I, R/N, R/F) in the time slots (1, 4) of the control channels. A mobile station desiring access to the system responds by sending a first message word (W1) in the time slot indicated by the base station in a first flag (B/I). When the mobile station (MS1) wishes to transmit several message words (W2, W3), the base station (BS) reserves one or more time slots to this end by transmitting the first flag (B/I), although this flag now states that these time slots are busy for other mobile stations (MS2, MS3). Furthermore, the base station transmits a flag (R/N) which states whether or not a message word has been received from the mobile station (MS1). The base station can transmit a further flag (R/F), which denotes that a given time slot has been reserved for a given mobile station (MS3) from the very beginning of an access procedure and cannot therefore be used by any other mobile station (MS1, MS2).

Soft handoff in a cellular telecommunications system

Abstract: A soft handoff in a cellular telecommunications system in which a user mobile station (30) relays user communication radio signals via at least two base stations (BS) to and from a controlling mobile exchange (MSC) connected to another system user. The relay of user information signals is performed by using digital frames carried on digital transmission connections (70-76, 80-86) in the uplink and downlink direction. The differential delay of the two or more terrestrial routes between the base stations and the exchange is compensated by a novel time alignement (TA) procedure. Each of the base stations sends time aligment request to the mobile exchange which performs the frame time alignement of the downlink transmissions by taking into account TA requests from all base stations.

A method and apparatus for regulating transmission power

Abstract: In a telecommunications system, a method and system for power regulation compares the received power to a target value at a receiving station to adjust the power of the transmitting station periodically or non-periodically. Calculation of the signal strength required at the transmitting station may be performed at either the transmitting or receiving station using the path loss between the respective stations. The target value may be a constant or a function of the distance from the base station or a function of the path loss between the transmitting and receiving station.