Showing papers on "Base station published in 1995"

A framework for uplink power control in cellular radio systems

Abstract: In cellular wireless communication systems, transmitted power is regulated to provide each user an acceptable connection by limiting the interference caused by other users. Several models have been considered including: (1) fixed base station assignment where the assignment of users to base stations is fixed, (2) minimum power assignment where a user is iteratively assigned to the base station at which its signal to interference ratio is highest, and (3) diversity reception where a user's signal is combined from several or perhaps all base stations. For the above models, the uplink power control problem can be reduced to finding a vector p of users' transmitter powers satisfying p/spl ges/I(p) where the jth constraint p/sub j//spl ges/I/sub j/(p) describes the interference that user j must overcome to achieve an acceptable connection. This work unifies results found for these systems by identifying common properties of the interference constraints. It is also shown that systems in which transmitter powers are subject to maximum power limitations share these common properties. These properties permit a general proof of the synchronous and totally asynchronous convergence of the iteration p(t+1)=I(p(t)) to a unique fixed point at which total transmitted power is minimized. >

Personal communications service using wireline/wireless integration

Abstract: The Advanced Intelligent Network (AIN) wireline system connects to and controls processing of calls to a Personal Communication Service subscriber's wireless handset via a home base station or a wireless communication network. Depending on its current location, the subscriber's handset automatically registers with the base station or with a mobility controller of the wireless network. A new registration with the base station when the handset comes within range causes that station to update the subscriber's home location register in a central data base of the AIN. Similarly, when a handset first registers with a mobility controller, that controller updates the subscriber's home location register in the central data base of the AIN. In response to calls directed to the subscriber, the AIN accesses the home location register to determine the current location where the handset is registered. The AIN then uses that data to route the call to the current location. In response to calls from the handset, the central data base provides instruction data to the land line network and/or a mobility controller to extend a requested special service to the calling subscriber.

An algorithm for combined cell-site selection and power control to maximize cellular spread spectrum capacity

Abstract: There is much current interest in spread spectrum wireless mobile communications and in particular the issue of spread spectrum wireless capacity. We characterize spread spectrum cellular capacity and provide a combined power control, cell-site selection algorithm that enables this capacity to be achieved. The algorithm adapts users' transmitter power levels and switches them between cell-sites, and it is shown that the algorithm converges to an allocation of users to cells that is optimal in the sense that interference is minimized. The algorithm is decentralized, and can be considered as a mechanism for cell-site diversity and handover. We provide numerical examples to show how effectively the algorithm relieves local network congestion, by switching users in a heavily congested cell to adjacent, less congested cells. >

Method and system for connecting cells and microcells in a wireless communications network

Abstract: A wireless communications system includes a number of clusters of repeaters wherein all repeaters within a cluster arc connected to a common hub via respective millimeter-wave radio links. Wireless signals received by the repeaters from end-user devices are transparently carried by the millimeter-wave radio links to respective hubs that act as concentrators for the repeaters. The hubs may be linked to a wireless network base station (in an outdoor setting) or alternatively to a server or a PBX (in an indoor environment) via a high-speed transmission facility, such as a fiber optic cable that is thus shared by all the repeaters.

Multiple mode personal wireless communications system

Abstract: A multiple mode, personal, wireless communications system exists within a radiotelephone network serving general customers and provides additional services to a select group of customers. The system uses handsets (32) which automatically switch between a standard cellular radiotelephone mode of operation (1901) and an enhanced cordless mode (1420) when the handsets (32) are within range of pico cells (26) that are interconnected to the public switched telephone network (20). Each pico cell is controlled via a framework of overlay cells (10b) that operates independently of the radiotelephone network and uses a unique control protocol on a small number of reserved cellular channels. Each pico cell consists of a spectrally dynamic, non-capturing, frequency agile, multi-purpose base station (26) provided at customer-selected locations to cooperate with the overlay cell framework. Each pico cell is capable of supporting multiple handsets (32) and using low power operation that achieves limited coverage. Each pico cell reduces traffic on the standard cellular radiotelephone network by independently handling registered handsets (32). An alternate line option module (22) provides wireless local interconnect capability to selectively route call traffic between land lines (24) and the standard cellular radiotelephone network. Service control units (12) and host stations (17) facilitate wireless activation and control of each pico cell and handset (32) via the overlay cell framework.

Integrated power control and base station assignment

Abstract: In cellular wireless communication systems, transmitted power is regulated to provide each user an acceptable connection while limiting the interference seen by other users. Previous work has focused on maximizing the minimum carrier to interference ratio (CIR) or attaining a common CIR over all radio links. However, previous work has assumed the assignment of mobiles to base stations is known and fixed. In this work, we integrate power control and base station assignment. In the context of a CDMA system, we consider the minimization of the total transmitted uplink power subject to maintaining an individual target CIR for each mobile. This minimization occurs over the set of power vectors and base station assignments. We show that this problem has special structure and identify synchronous and asynchronous distributed algorithms that find the optimal power vector and base station assignment. >

Multi-code CDMA wireless personal communications networks

Abstract: Proposes a code division multiple access (CDMA) based system that can provide a smooth migration path to PCS, either from a digital cellular system (IS-95) or from a wideband CDMA system, to serve both isochronous and asynchronous applications. A unified digital bandwidth on demand platform is realized by allocating multiple codes (on demand), and hence increased capacity, to users. This approach, dubbed multi-code CDMA (MC-CDMA), will enable efficient delivery of all services made possible by digital cellular, CDPD, and other PCS technologies. Since a large variety of services (voice, data, image, and perhaps video) is expected in future wireless networks, users with very different, and time-varying, source rates will have to be accommodated. MC-CDMA is a wireless system whose rate (which is proportional to the number of codes assigned to the user) and service are dynamically matched to users' needs and can evolve from commercial digital cellular systems. This system retains the CDMA advantage in combating multipath and does not require significant modifications of the radio frequency (RF) circuitry. The dynamic, packet-like capacity access enabled by MC-CDMA will allow users to access the base station at different source rates, and when all other users are idle, will provide peak rate access to a single user.

Remote antenna driver for a radio telephony system

Abstract: A multichannel radiotelephony system provides two way cordless communications with a plurality of multichannel transceivers portable within a coverage area comprised by a plurality of cells, each associated with a base station and antennas, such as to permit channel frequency reuse in cells within the coverage area. For at least part of the coverage area, the locations of the antennas within the cells and the locations of the base stations are independently mapped, the antennas being associated with active antenna systems and the active antenna systems being connected to the base stations utilizing broadband transmission by means of a fixed bi-directional signal distribution network. The network is connected to the base stations and the antenna systems through suitable interfaces incorporating frequency translation so that available frequency bands in the signal distribution network which will normally be shared with other services, may be utilised. Plural base stations may be co-located. The radio link to the transceivers may be frequency or time division multiplexed, but communication over the network will normally be frequency multiplexed, using separate bands for transmission and reception.

Medium access control scheme for wireless LAN using a variable length interleaved time division frame

Abstract: A Medium Access (MAC) Protocol is utilized for wireless access, preferrably over a radio frequency channel, for a plurality of remote stations to a base station on a LAN. The MAC protocol is based on a reservation scheme for user data traffic and a random access technique for control and signalling traffic. There is a time division frame structure in which time is slotted. Time slots are grouped into variable length periods. The variable frame structure consists of a frame header followed by interleaved periods of different types (type A, B or C). Type A periods are allocated to the outbound channel which is used for data transfer from the base station to the remote stations. Type B periods, are allocated to the inbound channel that is used for contention-free data transfer from the remote stations to the base station. Allocation of the data slots in the A and B periods is performed by the base station. Type C periods are reserved to the control channel used for transmission of reservation requests and data from the remote stations to the base station in a random-access contention mode using a slotted Aloha protocol. The duration and sequence of periods may be varied by using a technique for interleaving periods of different types. The base station estimates the number of actively transmitting remote stations utilizing feedback information from the remote stations. This estimate is broadcast to the remote stations as control indicia to control their transmission attempts in C slots, thus yielding high transmission efficiency.

Distributed architecture for a wireless data communications system

Abstract: A data communications system characterized by the combination of a base station connected to a plurality of repeaters for communicating with remote terminals in response to outgoing data from a host computer and for communicating with the host computer in response to incoming data from the remote terminals Each repeater is assigned a coverage area with in a predetermined communications area to support data communications with the remote terminals located within its coverage area In response to incoming data, a repeater conducts a signal amplification operation and outputs amplified incoming data to the base station via a first communications link The base station processes the amplified incoming data and, in turn, generates processed incoming data for distribution to the host computer via a second communications link The base station also processes the outgoing data from the host computer to generate processed outgoing data, and sends transmitted outgoing data to each repeater via the first communications link Each repeater connected to the base station can amplify the transmitted outgoing data, and outputs amplified outgoing data to the remote terminals within its coverage area

Reverse link, closed loop power control in a code division multiple access system

Abstract: The process of the present invention enables a mobile radiotelephone to operate at a 100% duty cycle while providing closed loop power control. The base station measures the signal to noise ratio of the signal from the mobile and compares that SNR with the SNR threshold values the base station has for each data rate the mobile is capable of transmitting. The base station then generates power control commands to instruct the mobile to change its power depending on the outcome of the comparisons.

Communication network having a plurality of bridging nodes which transmit a beacon to terminal nodes in power saving state that it has messages awaiting delivery

Abstract: An apparatus and a method for routing data in a radio data communication system having one or more host computers, one or more intermediate base stations, and one or more RF terminals organizes the intermediate base stations into an optimal spanning-tree network to control the routing of data to and from the RF terminals and the host computer efficiently and dynamically. Communication between the host computer and the RF terminals is achieved by using the network of intermediate base stations to transmit the data.

Distributed-queueing request update multiple access (DQRUMA) for wireless packet (ATM) networks

Abstract: In a wireless packet (ATM) network that supports an integrated mix of multimedia traffic, the channel access protocol needs to be designed such that mobiles share the limited communications bandwidth in an efficient manner: maximizing the utilization of the frequency spectrum and minimizing the delay experienced by mobiles. In this paper, we propose and study an efficient demand assignment channel access protocol, which we call distributed-queueing request update multiple access (DQRUMA). The protocol can be used for a wide range of applications and geographic distances. Mobiles need to send requests to the base station only for packets that arrive to an empty buffer. For packets that arrive to a non-empty buffer transmission requests are placed collision-free by piggybacking the requests with packet transmissions. The simulation results show that even with the "worst possible" traffic characteristics, the delay-throughput performance of DQRUMA is close to the best possible with any access protocol. In addition, explicit slot-by-slot announcement of the "transmit permissions" gives the base station a lot of control over the order in which mobiles transmit their packets.

Time division multiple access methods for wireless personal communications

Abstract: Time division multiple access (TDMA) is a classic approach to multiple access in digital cellular wireless communications systems. The authors summarize a number of frequency and time slot allocation techniques for enhancing the capacity and flexibility of TDMA-based systems. They also describe how the problems of fading, delay spread, time variability and interference affect TDMA systems, and how they may he countered and even exploited by appropriate techniques of detection, diversity, coding, adaptive equalization and slow frequency hopping (FH). It is worth emphasizing that the use of one of these techniques, slow random FH, results in a system that is in effect a hybrid of TDMA and code division multiple access (CDMA). >

Personal tracking system integrated with base station

Abstract: The personal tracking system including the intelligent position determining means coupled with the cellular phone and the base station is disclosed. The base station includes a computer, a modem, and a telephone. The computer further includes base station software for communicating with the mobile unit. The mobile unit transmits the location data to the base station at certain times and at certain locations.

AIRMAIL: a link-layer protocol for wireless networks

Abstract: This paper describes the design and performance of a link-layer protocol for indoor and outdoor wireless networks. The protocol is asymmetric to reduce the processing load at the mobile, reliability is established by a combination of automatic repeat request and forward error correction, and link-layer packets are transferred appropriately during handoffs. The protocol is named AIRMAIL (AsymmetrIc Reliable Mobile Access In Link-layer). The asymmetry is needed in the design because the mobile terminals have limited power and smaller processing capability than the base stations. The key ideas in the asymmetric protocol design consist of placing bulk of the intelligence in the base station as opposed to placing it symmetrically, in requiring the mobile terminal to combine several acknowledgments into a single acknowledgment to conserve power, and in designing the base stations to send periodic status messages, while making the acknowledgment from the mobile terminal event-driven. The asymmetry in the protocol design results in a one-third reduction of compiled code. The forward error correction technique incorporates three levels of channel coding which interact adaptively. The motivation for using a combination of forward error correction and link-layer retransmissions is to obtain better performance in terms of end-to-end throughput and latency by correcting errors in an unreliable wireless channel in addition to end-to-end correction rather than by correcting errors only by end-to-end retransmissions. The coding overhead is changed adaptively so that bandwidth expansion due to forward error correction is minimized. Integrity of the link during handoffs (in the face of mobility) is handled by window management and state transfer. The protocol has been implemented. Experimental performance results based on the implementation are presented.

Spectrally efficient high capacity wireless communication systems

Abstract: A wireless system includes a network of base stations (1) for receiving uplink signals transmitted from a plurality of remote terminals (69) and for transmitting downlink signals to the remote terminals. Each base station (1) includes a plurality of transmitting antenna elements (18) for transmitting downlink signals and receiving antenna elements (19) for receiving uplink signals, a signal processor (13) connected to the antenna elements for determining spatial signatures and multiplexing and demultiplexing functions. A multiple base station controller (66) is used for optimizing network performance.

The spectrum efficiency of a base station antenna array system for spatially selective transmission

Abstract: In this paper we investigate the spectrum efficiency gain using transmitting antenna arrays at the base stations of a mobile cellular network. The proposed system estimates the angular positions of the mobiles from the received data, and allows multiple mobiles to be allocated to the same channel within a cell. This is possible by applying a transmit scheme which directs nulls against co-channel users within the cell. It is shown that multiple mobiles per cell is an efficient way of increasing capacity in comparison with reduced channel reuse distance and narrow beams (without directed nulls). The effect of the spatial spread angle of the locally scattered rays in the vicinity of the mobile is also investigated. >

Method and apparatus for controlling power in a variable rate communication system

Abstract: A method and an apparatus for controlling transmission power in a variable rate communication system. A base station (30) monitors the reverse link signal transmitted from a mobile station (50). Base station (30) determines whether mobile station (50) should increase or decrease its power based either upon frame error rates detected by a decoder (44) or by the level of received signal power detected at a receiver (42). In response to this analysis, a control processor (46) generates a power control signal and transmits this signal to mobile station (30).

Multiple access cellular communication with dynamic slot allocation and reduced co-channel interference

Abstract: An apparatus and method reduces co-channel interference in multiple-access cellular communication systems in which frame time or frequency slots are allocated between uplink and downlink. An omnidirectional antenna or a set of directional antennas are used in each cell base station to communicate with users. The frame slots (710,715,720) in which the antennas communicate uplink and downlink information are arranged in accordance with a predetermined frame organization to reduce mixed co-channel interference (CCI). Mixed CCI occurs when a downlink transmission from one base station antenna in a given cell interferes with uplink reception in another base station antenna in a frequency reuse (FR) cell. A potentially-interfering antenna in a given cell is therefore directed to transmit downlink information in a different portion of the frame than that in which a potentially-interfered-with antenna in the frequency reuse cell receives uplink information. The frame slots may be allocated such that only a portion (720) of the available slots are dynamically allocated in accordance with user demand, while the remaining portions are assigned to either uplink (710) or downlink (715) communication.

Transmission power control method and a transmission power control apparatus

Abstract: A transmission power control method of a mobile station in a CDMA (Code Division Multiple Access) system which primarily controls transmission power of the mobile station by using a closed loop control which enables high accuracy power control. When the received power at the base station of a signal from the mobile station suddenly increases owing to the state of buildings surrounding the mobile station, the transmission power of the mobile station must be quickly reduced to prevent the interference to other mobile stations. The mobile station measures an average value of the received power per transmission power control period of a desired signal from the base station, and detects the difference ΔRSSI between the current average value and that of one of the previous transmission power control periods. If ΔRSSI exceeds a reference power difference ΔP th , transmission power P T corresponding to ΔRSSI is set by using an open loop transmission power control to quickly reduce the transmission power of the mobile station. If ΔRSSI is lower than ΔP th , the transmission power P T is determined in accordance with the transmission power control bit sent from the base station.

Wireless telephone distribution system with time and space diversity transmission

Abstract: A wireless communication system combines time and space diversity to reduce fading and simplify receiver design. In particular, a data packet which carries digital telephone traffic, is transmitted at three different times from three different antennas (A-C). The mobile subscriber receiver (10) thus receives the same data packet at three different times from three different antennas, and uses the best data packet or combination of the data packets to reduce the effects of fading. A transfer station (54, 56, 58) receives a time division multiplex multiple access (TDMA) signal from a base station carrying telephone data packet traffic to form three data packet repeats at spatially diverse antennas locations. The transfer station further modulates a code division multiple access (CDMA) system using a TDMA signal which links the mobile subscriber receiver to the transfer station. Each data packet received at the transfer station is thus retransmitted at three different times to the mobile subscriber station on a CDMA link.

Comprehensive mobile communications device registration method

Abstract: A comprehensive method for mobile station registration in a cellular communication system wherein registrations are made due to multiple stimulus. Registration can occur as a function of distance traveled since the previous registration. Registration can occur due to entering the coverage area of a base station assigned to a zone in which the mobile station has not recently registered. A registration timer can be used to ensure a minimum time between registrations. Registrations can occur at power up and at power down. The mobile station can be ordered to register by a transmission from a base station. Registration can occur due to parameter changes with in the mobile station. Registration may also occur through necessary communication with a base station which is not expressly directed to registration.

Signaling and control architecture for an ad-hoc ATM LAN

Abstract: The present invention is a signaling and control architecture for establishing a connection between mobile users in a wireless ATM LAN. The ATM LAN includes a plurality of portable base station (PBS) switching nodes coupled together to enable communication between said nodes, wherein the nodes are configurable in an arbitrary topology to form an ad-hoc network. The present invention includes network management techniques for configuration of data tables used for connection control. Mobility management techniques are disclosed to handle mobile sign-ons and idle handoffs, locate mobile users during connection and setup and perform handoffs when a mobile is actively involved in a connection. Connection control procedures are also included for setting up and releasing connections on demand.

Remote transmitter power control in a contention based multiple access system

Abstract: The power control process of the present invention enables a base station communicating over a forward packet channel to a mobile radio to control the power of the mobile radio transmitting over a reverse packet channel to the base station. The base station maintains a maximum energy per bit to total interference spectral density ratio threshold for the reverse channel as well as a desired threshold that results in a low frame error rate. By comparing each radiotelephone's estimated energy per bit to total interference spectral density ratio to the desired and maximum thresholds, power control commands to increase or decrease the radiotelephone's transmit power are generated depending on the outcome of the comparison.

Pilot signal searching technique for a cellular communications system

Abstract: An improved method and system for performing a pilot signal searching operation in anticipation of handoff in mobile station (18) communication between base stations (12, 14). The mobile station (18) maintains a list of Active Set pilot signals transmitted from base stations with which the mobile station is to communicate through, and a list of Neighbor Set pilot signals (N) from base stations within a predetermined proximity of the mobile station (18). The searching operation contemplates comparing pilot signal strength measurements corresponding to each base station entry within the Neighbor Set (N) to a first predetermined level. One or more entries from the Neighbor Set (N) having a base station signal strength measurement greater than the first predetermined level may be placed in the Pre-Candidate Set (PC). Tine strength of the pilot signals associated with entries in the Pre-Candidate Set (PC) are then further evaluated to determine eligibility within the Candidate Set (C), from which are selected the entries comprising the Active Set.

Airborne radiotelephone communications system

Abstract: The airborne radio communications system of the present invention enables an airborne radio to communicate with the ground based cellular radiotelephone system. The present invention also enables the ground based system to keep track of the location of the airborne radiotelephone and page it when a call from the ground based telephone system is received. The ground base station is connected to upward radiating antennas that form airborne cells. As the aircraft with the radio flies through the airborne cells, the airborne relay receives the signals from the base station and relays them to the radio. If the radio is transmitting signals, the relay transmits those signals, through the airborne cells, to the base station. As the aircraft moves from cell to cell, the radio is handed off to the next cell to maintain communications with the ground.

Efficient communication system using time division multiplexing and timing adjustment control

Abstract: A system for time division multiplexed communication over a single frequency band in which guard time overhead is reduced by active adjustment of reverse link transmission timing as a function of round trip propagation time. In one embodiment, during a first portion of a time frame, a base station issues a single burst segmented into time slots comprising data directed to each user station. After a single collective guard time, the user stations respond, one by one, in allocated time slots on the same frequency as the base station, with only minimal guard times between each reception. In order to prevent interference among the user transmissions, the base station measures the round trip propagation time for each user station and commands the user stations to advance or retard their transmission timing as necessary. To establish the initial range of a new user station, a short message is sent by the new user station during the collective guard portion (or, alternatively, during an available time slot), from which the base station calculates the propagation delay and hence the distance of the user station. Messages sent from the base station to the user stations may be interleaved so as to reduce the effects of potential noise or interference.

BAHAMA: a broadband ad-hoc wireless ATM local-area network

Abstract: We describe the theory, design and ongoing prototyping of a wireless ATM LAN/PBX capable of supporting mobile users with multi-Mb/s access rates and multi-Gb/s aggregate capacities. Our proposed LAN consists of network nodes called portable base stations (PBS) providing microcell coverage. The PBSs are designed to be low-cost, compact and high-speed and can be relocated conveniently. We employ a concept of ad-hoc networking in the layout of the PBS-to-PBS interconnection. That is, the PBSs can be distributed in an arbitrary topology to form a backbone network and can be reconfigured with relative ease. The PBS-to-PBS backbone links are high-speed (Gb/s) for supporting high system capacity. Although they can either be wired or wireless, our emphasis is on wireless implementations. The user-to-PBS links, on the other hand, are primarily for mobile access (e.g., 2-20 Mb/s) and therefore are wireless. Wired connections from stationary users to PBSs are also possible. Typical mobile users are assumed to be laptops or notebook computers. Services supported include conventional data applications (e.g., over TCP/IP or SPX/IPX) as well as multimedia (video, voice and data) applications with QoS (quality-of-service) guarantees. A "aireless ATM" concept is proposed so as to provide seamless internetworking with other wired ATM local and wide-area networks. Algorithms and control in our network are highly distributed for simple implementations and ease of mobility management. A new wireless VP/VC concept and a homing algorithm are described to provide ATM cell routing and connections in the network. PBS hardware and software architectures are discussed. Call management, network management and signaling are designed for simplicity, high performance and modular implementations. A fast network restoration scheme is proposed to cope with the potential link or node failures in the ad-hoc network. Error control is addressed taking the unreliable wireless links into consideration. Finally, a prototyping project called BAHAMA (broadband ad hoc ATM anywhere) for demonstrating this network concept is briefly outlined.

PCS pocket phone/microcell communication over-air protocol

Abstract: A simple and flexible over-air protocol for use with a mobile telephone system, having hand-held telephones (102) in a microcell or other type of cellular communication system. A method in which user stations (102) communicate with one or more base stations (104) to place and receive telephone calls, in which the user stations (102) are provided a secure voice or data link and have the ability to handoff calls between base stations (104) while such calls are in progress. Each base station (104) has a set of 'air channels' to which it transmits in sequence. The air channels supported by each base station (104) are called that base station's polling loop. A user station (102) receives general polling information on an unoccupied air channel, transmists responsive information to the base station, and awaits acknowledgement from the base station. Each base station (104) may therefore simultaneously maintain communication with as many user stations (102) as there are air channels in its polling loop. The ability of a user station (102) to communicate on any unoccupied air channel makes the protocol air-channel agile, while the stability of user station and base station clocks may define air channels, gaps, and minor frames.