Showing papers on "Telecommunications link published in 2001"

Enhancing the cellular downlink capacity via co-processing at the transmitting end

Abstract: A linear pre-processing plus encoding scheme is proposed, which significantly enhances cellular downlink performance, while putting the complexity burden on the transmitting end. The approach is based on LQ factorization of the channel transfer matrix combined with the "writing on dirty paper" approach (Caire, G. and Shamai, S., Proc. 38th Annual Allerton Conference on Communication, Control and Computing, 2000) for eliminating the effect of uncorrelated interference, which is fully known at the transmitter but unknown at the receiver. The attainable average rates with the proposed scheme approach those of optimum joint processing at the high SNR region.

Repeaters for wireless communication systems

Abstract: A repeater and associated method of use includes at least one antenna element for communicating in one direction and at least one antenna element for communicating in another direction. A radio frequency uplink path and a radio frequency downlink path are coupled between the antennas. At least one of the radio frequency uplink path or the radio frequency downlink path includes an adaptive cancellation circuit. The adaptive cancellation circuit is configured to generate a cancellation signal without requiring an injected signal. The cancellation signal, when added to a radio frequency signal in the respective uplink and downlink paths, substantially reduces feedback signals present in the radio frequency signal.

A transmitter diversity scheme for wideband CDMA systems based on space-time spreading

Abstract: We present a transmit diversity technique for the downlink of (wideband) direct-sequence (DS) code division multiple access (CDMA) systems. The technique, called space-time spreading (STS), improves the downlink performance by using a small number of antenna elements at the base and one or more antennas at the handset, in conjunction with a novel spreading scheme that is inspired by space-time codes. It spreads each signal in a balanced way over the transmitter antenna elements to provide maximal path diversity at the receiver. In doing so, no extra spreading codes, transmit power or channel information are required at the transmitter and only minimal extra hardware complexity at both sides of the link. Both our analysis and simulation results show significant performance gains over conventional single-antenna systems and other open-loop transmit diversity techniques. Our approach is a practical way to increase the bit rate and/or improve the quality and range in the downlink of either mobile or fixed CDMA systems. A STS-based proposal for the case of two transmitter and single-receiver antennas has been accepted and will be included as an optional diversity mode in release A of the IS-2000 wideband CDMA standard.

A multicarrier CDMA architecture based on orthogonal complementary codes for new generations of wideband wireless communications

Abstract: This article is a review of our ongoing research effort to construct a new multicarrier CDMA architecture based on orthogonal complete complementary codes, characterized by its innovative spreading modulation scheme, uplink and downlink signaling design, and digital receiver implementation for multipath signal detection. There are several advantages of the proposed CDMA architecture compared to conventional CDMA systems pertinent to current 2G and 3G standards. First of all, it can achieve a spreading efficiency (SE) very close to one (the SE is defined as the amount of information bit(s) conveyed by each chip); whereas SEs of conventional CDMA systems equal 1/N, where N denotes the length of spreading codes. Second, it offers MAI-free operation in both upand downlink transmissions in an MAI-AWGN channel, which can significantly reduce the co-channel interference responsible for capacity decline of a CDMA system. Third, the proposed CDMA architecture is able to offer a high bandwidth efficiency due to the use of its unique spreading modulation scheme and orthogonal carriers. Lastly, the proposed CDMA architecture is particularly suited to multirate signal transmission due to the use of an offset stacked spreading modulation scheme, which simplifies the rate-matching algorithm relevant to multimedia services and facilitates asymmetric traffic in up- and downlink transmissions for IP-based applications. Based on the above characteristics and the obtained results, it is concluded that the proposed CDMA architecture has a great potential for applications in future wideband mobile communications beyond 3G, which is expected to offer a very high data rate in hostile mobile channels.

Uplink power control algorithm

Abstract: In a system having a base station transmitter for transmitting data blocks to one or more mobile stations over a radio link, there is a method for determining an uplink transmit power level at which to transmit a current data block over a radio link from the mobile to the base transmitter station The method evaluates airlink quality measurements in the radio link over a measurement interval, wherein each time a message is sent to the mobile station, it is evaluated whether a specified number of uplink blocks have transmitted by the mobile station since the start of the measurement interval Based on the evaluated airlink quality measurement, the method determines the uplink transmit power level that the mobile should be using for the current block, and adjusts the transmit power level, if necessary, for the current block

Method for optimizing the random access procedures in the cdma cellular networks

Abstract: The disclosed invention is referred to a method for optimising the random access procedures in third generation CDMA cellular telephony systems. The particular embodiment of the example concerns a TD-SCDMA-TDD synchronous realization. The disclosed procedure includes a preliminary part charged to the network (BSSC, MSC) only for establishing the following associations between the configuration parameters of the involved physical channels: one signature burst (SYNC1) is associated to one forward access channel (P-FACH) only, in order to avoid any ambiguity in the mobile stations about where to look for the expected acknowledgement from the network; one random access common channel (P-RACH) is associated to one forward access channel (P-FACH) only, in order to reduce collision on the latter (P-RACH); one access grant channel (P/S-CCPCH, AGCH) only is associated to one random access common channel (P-RACH), in order to avoid any ambiguity in the mobile stations about where to look for the expected answer from the network with the indication of the dedicated service channels (DPCH); and each complete associative link binding the involved physical channels is included in the system information and broadcasted into the serving cell to be read by the mobile stations (MS, UE) when entering an actual part of the procedure charged to exchange protocol messages with the network (BSSC; MSC) through said associative links that being signalling at once to the mobile stations the route towards the services offered by the network, simplifying the access procedure consequently. Suitable groupings among: Downlink pilot sequences, Uplink pilot sequences, scrambling codes, basic midambles, are carried out in a cell-discriminating way and broadcasted into the cell to simplify the serving cell selection procedure.

Low-power hand-held transaction device

Abstract: An electronic hand-held device and method for inputting and sending requests and for receiving and outputting responses to the requests. The electronic hand-held device is a coupled to a telecommunications link over which requests are sent and responses are received. The electronic hand-held device can input request data in any number of different information media, including audio tones and voice signals, mechanical input to a keypad, printed bar codes, magnetic data stored in credit cards, and electronic data stored in electronic smart cards. The electronic hand-held device can output responses through an audio speaker, a visual LCD display device, and, optionally, through other output devices including printers. The electronic hand-held device is especially well suited for order entry and acquisition of product information.

Downlink channel covariance matrix (DCCM) estimation and its applications in wireless DS-CDMA systems

Abstract: The downlink channel covariance matrix (DCCM) is of vital importance in determining downlink beamforming weights for base station (BS) antenna array systems. For the frequency-division-duplex (FDD) mode, DCCM is difficult to obtain due to a lack of direct measurement of downlink channel responses. In this paper, a novel technique is proposed for estimating DCCM using uplink channel responses only, which does not need direction-of-arrival (DOA) estimation and its association. The downlink beamforming scheme is then proposed for wireless DS-CDMA systems, using the obtained DCCM information together with the so-called virtual uplink beamforming and power control technique. Computer simulations show that using the BS antenna array together with this new beamforming technique can provide larger system capacity than traditional DOA-based approaches, which just direct the main beam toward the desired user.

Method and system for a remote downlink transmitter for increasing the capacity and downlink capability of a multiple access interference limited spread-spectrum wireless network

Abstract: The present invention relates to a system and method for extending the coverage area and communication capacity of a spread-spectrum based wireless network. The system comprises a unique dual-scale, asymmetrical cellular architecture for a wireless network, wherein the communication uplink is based on a macro-cellular system, and the communication downlink is based on a micro-cellular system. Through the user of remote downlink transmitters in the micro-cellular system, the present invention provides a cost effective solution for increasing communication capacity, extending coverage area, and providing high speed communication downlink.

Scheduling transmission of data over a transmission channel based on signal quality of a receiver channel

Abstract: Data traffic is selectively transmitted in one direction when the quality or condition of the channel in the opposite direction is sufficient to ensure a reasonable or high likelihood that the transmitter will accurately receive and decode feedback messages. In one preferred, non-limiting, example embodiment, a base station schedules transmission of data packets to a user equipment unit (UE) over a downlink traffic channel when the uplink channel over which the UE sends ARQ type signals to the base station has a signal-to-interference ratio (SIR) greater than a predetermined threshold. The downlink channel condition is also preferably taken into account.

Resource pooling and effective bandwidths in CDMA networks with multiuser receivers and spatial diversity

Abstract: Much of the performance analysis on multiuser receivers for direct-sequence code-division multiple-access (CDMA) systems is focused on worst case near-far scenarios. The user capacity of power-controlled networks with multiuser receivers are less well-understood. Tse and Hanly (see ibid., vol.45, p.541-657, 1999) have shown that under some conditions, the user capacity of an uplink power-controlled CDMA cell for several important linear receivers can be very simply characterized via a notion of effective bandwidth. We show that these results extend to the case of antenna arrays. We consider a CDMA system consisting of users transmitting to an antenna array with a multiuser receiver, and obtain the limiting signal-to-interference (SIR) performance in a large system using random spreading sequences. Using this result, we show that the SIR requirements of all the users can be met if and only if the sum of the effective bandwidths of the users is less than the total number of degrees of freedom in the system. The effective bandwidth of a user depends only on its own requirement. Our results show that the total number of degrees of freedom of the whole system is the product of the spreading gain and the number of antennas. In the case when the fading distributions to the antennas are identical, we show that a curious phenomenon of "resource pooling" arises: the multiantenna system behaves like a system with only one antenna but with the processing gain the product of the processing gain of the original system and the number of antennas, and the received power of each user the sum of the received powers at the individual antennas.

Terrestrial digital multimedia/television broadcasting system

Abstract: A system for transmitting information as frames in digital format between users on a network using a single frequency and TDMA and/or CDMA communications. Broadcasting, multicasting and unicasting are provided, and communications may be part of a downlink and/or an uplink signaling scheme that allows user-user and user-central station communication. A synchronization segment or pre-amble for a frame may include identification of the source and/or the intended recipient. Walsh, Haar, Rademacher coding of selected frame components, among others, can be incorporated. Reed Solomon encoding, signal interleaving and intra-leaving, trellis encoding and turbo encoding are used for error detection and correction. The system provides two-way communication with the Internet and/or with a cellular network and/or for smaller networks of users.

The evolution of WCDMA towards higher speed downlink packet data access

Abstract: The first step of evolving WCDMA towards higher data rates is discussed. It is shown how techniques such as fast link adaptation, fast hybrid ARQ and fast scheduling, among others, can be applied to WCDMA, leading to increased throughput, lower delays, and downlink peak rates in the order of 10 Mbit/s. Through system simulations, the packet-data performance of such an evolved WCDMA system is illustrated.

Broadband communication system for mobile users in a satellite-based network

Abstract: A satellite-based communications system operating at high data rates includes a plurality of satellites each having uplink and downlink antennas for transmitting and receiving a plurality of signals utilizing a plurality of spot beams to and from a plurality of coverage areas at a predetermined range of frequencies. The system can include, or be combined with, other systems to enable increased capacity over high population areas and ubiquitous coverage over lower population areas. A portable antenna assembly can be coupled to a user's portable or mobile electronic device for coupling the electronic device directly to a satellite. A routing switch provides routing and switching on-board the satellite and routes signals according to their desired destination.

Dynamic channel allocation in multiple-access communication systems

Abstract: Dynamic allocation of communication channels among communication units (CU) in a communications system. Dynamic channel allocation employs a reservation set for reserving channels and an allocation set corresponding to the reservation set for receiving allocated channels. The reservation set and the allocation set are changed dynamically as a function of network parameters to control the dynamic channel operation. Reservation set information is broadcast downlink to multiple users to reserve an allocation set of uplink radio resources for specific ones of the users. The system uses a modification of the packet data channel (PDCH) of a GPRS/EGPRS or EDGE system which employs an Uplink Status Flag (USF) on each PDCH downlink radio block. The downlink reservation set information is commonly received by all users in the group of users. Allocation delay, bandwidth efficiency and other system parameters are optimized.

Method to control uplink transmissions in a wireless communication system

Abstract: Efficient data communication in wireless communication system is provided by using centralized control of data communications, such as packet switched services, over the uplink channel (mobile station (MS) to base station (BS)). A multiple access protocol is used where packet data mobile stations make requests for uplink channel resources. The request messages transmitted by the MSs inform the BS of service parameters. Examples of such service parameters are available transmit power at the MS, the amount of data to transmit and Quality of Service (QoS). The BS then processes the received request messages and performs interference management calculations to determine the portion of the BS's receive power budget that can be allocated to the data user requesting service. These calculations are used to control the amount of interference seen at the base station, to assign a data rate to the user and to aid scheduling algorithms in computing service order priorities. Any scheduling algorithm may be used; for example, scheduling may be based on the amount of data to be transmitted, the age of the data or the service priority associated with the mobile station. The interference control is used to prevent the occurrence of catastrophic levels of interference while maximizing the utilization of resources on the uplink.

Asymmetric measurement-based dynamic packet assignment system and method for wireless data services

Abstract: A method and system for assigning downlink and uplink channels to a mobile station registered with a base station, which uses an interference-sensing scheme and which provides improved reliability and performance over conventional schemes.

Joint power control and intracell scheduling of DS-CDMA nonreal time data

Abstract: The performance of DS-CDMA systems depends on the success in managing interference arising from both intercell and intracell transmissions. Interference management in terms of power control for real time data services like voice has been widely studied and shown to be a crucial component for the functionality of such systems. In this work we consider the problem of supporting downlink nonreal time data services, where in addition to power control, there is also the possibility of controlling the interference by means of transmission scheduling. One such decentralized schedule is to use time division so that users transmit in a one-by-one fashion within each cell. We show that this has merits in terms of saving energy and increasing system capacity. We combine this form of intracell scheduling with a suggested distributed power control algorithm for the intercell interference management. We address its rate of convergence and show that the algorithm converges to a power allocation that supports the nonreal time data users, using the minimum required power while meeting requirements on average data rate. Numerical results indicate a big potential of increased capacity and that a significant amount of energy can be saved with the proposed transmission scheme.

Space-time block-coded multiple access through frequency-selective fading channels

Abstract: Mitigation of multipath fading effects and suppression of multiuser interference (MUI) constitute major challenges in the design of wide-band third-generation wireless mobile systems. Space-time (ST) coding offers an effective transmit-antenna diversity technique to combat fading, but most existing ST coding schemes assume flat fading channels that may not be valid for wide-band communications. Single-user ST coded orthogonal frequency-division multiplexing transmissions over frequency-selective channels suffer from finite-impulse response channel nulls (fades). Especially multiuser ST block-coded transmissions through (perhaps unknown) multipath present unique challenges in suppressing not only MUI but also intersymbol/chip interference. In this paper, we design ST multiuser transceivers suitable for coping with frequency-selective multipath channels (downlink or uplink). Relying on symbol blocking and a single-receive antenna, ST block codes are derived and MUI is eliminated without destroying the orthogonality of ST block codes. The system is shown capable of providing transmit diversity while guaranteeing symbol recovery in multiuser environments, regardless of unknown multipath. Unlike existing approaches, the mobile does not need to know the channel of other users. In addition to decoding simplicity, analytic evaluation and corroborating simulations reveal its flexibility and performance merits.

Method for adaptively setting transmission parameters for a random access channel transmission uplink procedure in a wireless communication system

Abstract: The present invention provides a method to enhance the RACH message transmission of a wireless communication systems. Therefore the known RACH procedure for uplink transmission is extended by additional steps in order to allow the usage of adaptive transmission parameters for uplink transmissions, preferably the usage of adaptive modulation and coding (AMC). This is advantageous because studies in high-speed downlink packet access showed the possibility to increase the data rate of a downlink shared channel. The method according to the invention introduces a new RACH message preamble and enables the base station to estimate a suitable adaptive transmission parameters like AMC setting according to the current transmission conditions which is used during the RACH message transmission.

HARQ method in a CDMA mobile communication system

Abstract: Disclosed is a method for transmitting packet data and side information including a sequence number of the packet data in a CDMA mobile communication system employing a HARQ scheme for performing retransmission in response to a retransmission request message after initial transmission. The method comprises transmitting the packet data and the side information over a dedicated channel during the initial transmission; and transmitting the packet data and the side information over a common channel during the retransmission. The dedicated channel is a dedicated physical channel (DPCH), and the common channel is a physical downlink shared channel (DSCH).

IP platform for advanced multipoint access systems

Abstract: In LMDS systems the downlink bandwidth is continuously varying in time because each downlink burst uses a network termination individual modulation and coding (Physical layer) scheme, the higher layer (IP) functions cannot perform service priority respecting traffic shaping. The invention proposes mainly to combine both framing and IP layer functions within one inter-layer framer. The combination of both information ensures QoS provisioning in case of multi-modulation and multi-coding environment. The QoS queue server gets always informed on the actual amount of available data frame bits from the downlink framer and therefore, the QoS queue server is able to decide on the next IP packet or packet fraction to transport. This decision is always based on service priority aspects. As soon as the downlink frame is filled—supposing that the maximum downlink frame rate is always lower than the internal processing in the inter-layer framer—the QoS server stops the data delivery.

Cooperative polling in a wireless data communication system having smart antenna processing

Abstract: A method, communication device, and machine-readable medium. The method includes sending a first poll from a first base station having a smart antenna system to a first user terminal. The first base station receives a first uplink response signal from the first user terminal as a result of the first user terminal successfully receiving the first poll. The first base station also receives at least one other uplink response signals as a result of at least one other remote user terminal successfully receiving a second poll from a second base station. The first base station transmits downlink data to the first user terminal using a downlink smart antenna processing strategy for transmitting to the first user terminal, including mitigating interference to the first and one or more other remote communication devices from which the first base station received a first or other uplink response signal and that may be receiving during transmission of downlink data to the first user terminal. The downlink smart antenna processing strategy is using the first and other received uplink response signals. The first base station uses a first protocol with its associated user terminals and the second base stations uses a second protocol that is coordinated with the first protocol to enable the first base station to receive the first and other uplink response signals from second and one or more other remote communication devices that may be receiving during the step of transmitting downlink data to the first user terminal.

System, method and apparatus for facilitating resource allocation in a communication system

Abstract: A system, method, and apparatus for the efficient allocation of dedicated and/or shared downlink communication channels for packet data users in a communication system (100). The present invention provides a switching scheme in which users which are close to a base station (120a, 120b, 220a, 220b) are allocated a downlink shared channel in order to save channelization codes in the system (100, 200), whereas users that are far from a base station (120a, 120b, 220a, 220b) are allocated a downlink dedicated channel in order to conserve transmission power.

Uplink timing synchronization and access control for a multi-access wireless communication system

Abstract: Improved timing synchronization and access control techniques for use in an orthogonal frequency division multiplexed (OFDM) wireless system or other type of wireless communication system. In accordance with the invention, an uplink synchronization and access control system is provided in which mobile stations transmit certain timing and access signals in dedicated intervals in an uplink stream. Access control is illustratively implemented as a two-stage process in which a given mobile first transmits a generic uplink access signal in one of the intervals. If this access is accepted, the base station transmits an access acknowledgment containing initial timing and power corrections, along with initial channel assignments on which the mobile can initiate a call set-up process. For re-synchronization, mobiles transmit timing synchronization signals in the dedicated timing and access intervals. The base station measures the arrival time of the signals, and sends back appropriate timing corrections. The invention thereby ensures that orthogonality between mobiles is maintained.

Diversity system and method in a satellite telecommunication network

Abstract: A single uplink signal burst from a user terminal in an uplink region of a satellite radiotelephone system is received during an uplink signal frame at two or more visible satellites in the uplink region. The single received signal burst from the user terminal that is received at the two or more satellites then is diversity combined. The two or more satellites preferably receive a single uplink signal burst from a plurality of, and preferably all of, the user terminals in the uplink region without time overlap, so that diversity combining may be performed. Most preferably, all of the satellites receive signal bursts from all of the user terminals in the uplink region during the uplink signal frame, without time overlap, so that return link diversity combining using all of the visible satellites may be obtained. In order to allow reception by two or more visible satellites in the return link, of signal bursts from multiple user terminals in the uplink region, a guard time is established between adjacent uplink signal bursts that are transmitted from the user terminals in the uplink region. The guard time is based upon a time of arrival difference for the adjacent uplink signal bursts to one of the satellites, for example having lowest elevation angle or at the horizon. Fixed or variable guard times may be provided between adjacent uplink signal bursts that are transmitted from user terminals in the uplink region. Thus, the satellite radiotelephone system preferably can utilize all of the transmitted signals from the user terminals, to allow improved reception by the satellite and/or reduced power consumption by the user terminals.

Method for seamless inter-frequency hard handover in radio communication system

Abstract: A method for seamless inter-frequency hard handover in a radio communication system is disclosed. The method for seamless inter-frequency hard handover includes the steps of: a) at a mobile station, blocking a first uplink carrier frequency used for communication, transmitting a direct sequence spread preamable signal through a second uplink carrier frequency for a short time, and continuously performing the communication through the first uplink carrier frequency: and h) at a target base transciever station, acquiring an uplink synchronization of a mobile station based on the preamble before performing handover.

Apparatus and method for transmitting tfci used for dsch in a w-cdma mobile communication system

Abstract: Disclosed is a method for determining transmission power of a second TFCI bit indicating transport format information of data on a downlink shared channel transmitted from a selected Node B to a UE in a mobile communication system including the UE existing in a handover zone and a plurality of Node Bs in an active set of the UE. The Node Bs transmit dedicated channel data including a first TFCI bit to the UE over dedicated channels. A first Node B transmits dedicated channel data over a dedicated channel and transmits downlink shared channel data over the downlink shared channel. The first Node B determines a transmission power level of the second TFCI bit to be higher than a ratio of transmission power of the dedicated channel data from a Node B transmitting only the dedicated channel data to transmission power of the first TFCI bit.

Apparatus and method for acquiring an uplink traffic channel in wireless communications systems

Abstract: Uplink traffic channel allocation is realized by utilizing a dedicated control channel in which a prescribed portion of the control channel resource, for example, frequency, time slot or the like, is reserved for transporting the uplink traffic channel requests. Both the base station and the particular mobile unit know the prescribed portion of the control channel resource a priori. Consequently, when the particular mobile unit transmits an uplink traffic channel request via the prescribed portion of the control channel resource there is no need for adding any control header information, thereby minimizing overhead. Furthermore, the length of the uplink traffic channel requests can be optimally chosen without constraints imposed by other control message schemes. Reduced overhead coupled with the prescribed portion of the control channel resource arriving quite frequently reduces latency in the particular mobile unit acquiring an uplink traffic channel. In one example, delivery of adequate uplink traffic channel request information to the base station, while minimizing the adverse impact of losing requests, is ensured by persistently transmitting the requests. Specifically, after the mobile unit transmits a first request, it transmits a second or even a third request instead of waiting to receive a response message from the base station and/or waiting for a timer to time out. By the mobile unit using such a persistent request transmission scheme, the base station can readily determine the true value of the received request by eliminating the transmission loop delay effect, thereby allowing a sensible assignment decision to be made.

Dual mode uplink/downlink location measurement and multi-protocol location measurement

Abstract: Certain aspects of the disclosure relate to combining uplink and downlink location technologies into a single location-service system, to obtain the benefits offered by both of technologies while eliminating many of their individual shortcomings. Mobile devices that support downlink can then be located using the downlink mode, and mobile devices that do not support downlink can be located using the uplink mode. A mobile device may even be located based on a combination of uplink measurements and downlink measurements. Other aspects of the disclosure relate to providing a single location-service system to locate mobile devices that communicate using a plurality of different communication protocols.