Showing papers on "Channel allocation schemes published in 1997"

Adaptive channel allocation method and apparatus for multi-slot, multi-carrier communication system

Abstract: A method and system of adaptive channel allocation in a multi-carrier, multi-slot system (220) is provided. In the method and system a subset of M channels is chosen from a larger set of N channels available for communications on a link (300, 330). As communications take place on the link (300, 330), signal quality (C/I) measurements on the channels of the subset of M channels and interference (I) measurements on the channels of the group of N channels are periodically performed. The C/I and I measurements are then used to reconfigure the subset of M channels to reduce co-channel interference on the link (300, 330).

Adaptive resource allocation for prioritized call admission over an ATM-based wireless PCN

Abstract: In future personal communications networks (PCNs) supporting network-wide handoffs, new and handoff requests will compete for connection resources in both the mobile and backbone networks. Forced call terminations due to handoff call blocking are generally more objectionable than new call blocking. The previously proposed guard channel scheme for radio channel allocation in cellular networks reduces handoff call blocking probability substantially at the expense of slight increases in new call blocking probability by giving resource access priority to handoff calls over new calls in call admission control. While the effectiveness of a fixed number of guard channels has been demonstrated under stationary traffic conditions, with nonstationary call arrival rates in a practical system, the achieved handoff call blocking probability may deviate significantly from the desired objective. We propose a novel dynamic guard channel scheme which adapts the number of guard channels in each cell according to the current estimate of the handoff call arrival rate derived from the current number of ongoing calls in neighboring cells and the mobility pattern, so as to keep the handoff call blocking probability close to the targeted objective while constraining the new call blocking probability to be below a given level. The proposed scheme is applicable to channel allocation over cellular mobile networks, and is extended to bandwidth allocation over the backbone network to enable a unified approach to prioritized call admission control over the ATM-based PCN.

Area spectral efficiency of cellular mobile radio systems

Abstract: We consider the average area spectral efficiency (ASE) of variable-rate transmission cellular mobile systems. This efficiency is defined as the sum of the maximum average data rates/Hz/unit area supported by a cell's base station. We study this efficiency as a function of the reuse distance for the uplink of FDMA and TDMA systems under different interference configurations. Results indicate that, based on the worst-case interference configuration, the optimal reuse distance is approximately four. However, this optimal reuse distance is two for the best-case and the average interference configurations (i.e. frequencies should be reused every cell). In addition, the ASE decreases as an exponential of a 4th order polynomial relative to the cell size. This result quantities exactly how much cellular system capacity increases with decreased cell size. We also quantify the increase in ASE due to antenna sectorization. We conclude by analyzing the effect of traffic loading on the ASE when a fixed channel assignment is employed.

Radio resource management in future wireless networks: requirements and limitations

Abstract: Comparing market estimates for wireless personal communication and considering proposals for wideband multimedia services with the existing spectrum allocations for these types of systems show that spectrum resource management remains an important topic in the near and distant future. In this article the authors start by presenting a quite general formulation of the radio resource management problem where the three key allocation decisions are concerned with waveforms ("channels"), access ports (or base stations), and, finally, with transmitter power. Some approaches to these problems found in the literature are reviewed. In particular, the principles of random channel allocation schemes, as found in frequency-hopping or direct-sequence CDMA systems, are compared with deterministic dynamic channel allocation schemes. The article closes by giving an outlook of some of the key problems in resource management in future wireless multimedia systems.

Mobile power management for wireless communication networks

Abstract: For fixed quality-of-service constraints and varying channel interference, how should a mobile node in a wireless network adjust its transmitter power so that energy consumption is minimized? Several transmission schemes are considered, and optimal solutions are obtained for channels with stationary, extraneous interference. A simple dynamic power management algorithm based on these solutions is developed. The algorithm is tested by a series of simulations, including the extraneous-interference case and the more general case where multiple, mutually interfering transmitters operate in a therefore highly responsive interference environment. Power management is compared with conventional power control for models based on FDMA/TDMA and CDMA cellular networks. Results show improved network capacity and stability in addition to substantially improved battery life at the mobile terminals.

Channel frequency allocation for multiple-satellite communication network

Abstract: A method and apparatus (system) for providing forward-link channel-frequency allocation for multiple-satellite cellular communications networks is disclosed. The system has a centralized ground-operations control center that provides bi-weekly minute-by-minute allocation plans for geographically-defined service areas. This enables each service area to set its diversity policy in accordance with the requirements of the government regulators and customer preferences within the service area. The system has a user model having a frequency re-use pattern, a channel allocation model for modelling the power allocated to each channel, and a gateway channel model for allocating channels in accordance with the user model and the channel allocation model. The allocation is made for each satellite of the plurality of satellites. The traffic allocation induces an operating frequency for each of the one or more links in each satellite of the plurality of satellites. The satellite communication system computed frequency allocation is optimized to minimize total radiation from all forward links for one or more of the plurality of satellites.

Channel reuse strategies for indoor infrared wireless communications

Abstract: We examine systems of fixed-channel reuse for base stations in an indoor infrared wireless communication system. The following techniques are compared: time-division multiple access (TDMA) using on-off keying (OOK) or pulse-position modulation (PPM); frequency-division multiple access (FDMA) using binary phase-shift keying (BPSK) or quadrature phase-shift keying (QPSK); code-division multiple access (CDMA) using OOK with direct-sequence spreading by m-sequences or optical orthogonal codes (OOCs). We define a parameter /spl gamma/, which equals the signal-to-noise ratio (SNR) for unit optical path gain and is proportional to the square of the transmitted average optical power. Using measured pathloss data, it is found that in a system using hexagonal cells and a reuse factor of three, for cell radii above 3 m, TDMA with OOK or 2-PPM, and CDMA using OOCs all require approximately the same /spl gamma/ to achieve a worst-case bit-error rate (BER) of 10/sup -9/ within a cell. Using TDMA with 4-PPM results in a 6-dB decrease in the required value of /spl gamma/. CDMA using m-sequences requires an increase in /spl gamma/ of 5 dB over TDMA using OOK, and FDMA with BPSK requires an increase of 12 dB. For a given reuse factor N in the noise-limited regime, the required value of /spl gamma/ decreases in inverse proportion to N/sup 2/ for TDMA schemes and inversely with N for FDMA and CDMA schemes. For cell radii below 3 m, cochannel interference dominates the systems using TDMA, FDMA, and CDMA with an OOC, resulting in an irreducible BER above 10/sup -9/ at cell radii below 1.5 m. Only CDMA with m-sequences does not develop an irreducible BER, making it the only choice for cell radii below 1.5 m.

Application of dynamic channel allocation strategies to the GSM cellular network

Abstract: We refer to the implementation and the performance of a specific class of dynamic carrier allocation (DCA) strategies which is suitable for being introduced in the pan-European Global System for Mobile communications (GSM) cellular network. One of the main concerns of this work is to verify if and to what extent strategies belonging to this class can offer better performance than fixed channel allocation (FCA) in realistic traffic and propagation conditions. The impact of the introduction in a real network of two of the more promising DCA strategies in the considered class is assessed. In particular, solutions are presented concerning the signaling exchanges entailed by the implementation of each of the considered DCA strategies. A performance evaluation of a realistic cellular network exploiting the above-mentioned DCA strategies is carried out, taking into account all of the main GSM transmission and network aspects. The simulations have been performed by considering a realistic cell layout corresponding to the urban area of Rome, its realistic propagation environment, and a user mobility model based on the building percentages in such an area. The results of the performance evaluation show that, by carefully choosing the values of the parameters characterizing each of the considered DCA strategies, a conspicuous increase in the number of users supported by the cellular network can be achieved.

A study on a channel allocation scheme with an adaptive array in SDMA

Abstract: This paper describes spatial division multiple access (SDMA) using an adaptive array. A spatial correlation coefficient is proposed as a criterion to determine the possibility of duplicate channel allocation. When the average input SNR is more than 20 dB, the users satisfying a correlation coefficient of less than 0.9 can be accommodated in the same channel in a 2-user SDMA model with a 2-element adaptive array. The blocking rate performance shows that this 2-user SDMA can improve channel efficiency almost twice.

Intelligent dynamic channel allocation scheme for a mobile communications network

Abstract: Intelligent allocation of wireless resources can help avoid the problems of dropped calls in a mobile communications network. A service for allocating resources is designed to develop profiles of subscribers' mobility. That is, profiles are developed for routes, traveled by subscribers at certain days and times. For example, some subscribers commute to and from work at relatively fixed times. By compiling this information in the profile and tracking the movement of the subscriber, the mobile network can anticipate the subscriber's movement into a next cell. Thus, wireless resources in the next cell can be reserved prior to the anticipated handover of an ongoing call involving the subscriber. Thus, uninterrupted service can be maintained and dropped calls can be avoided.

Telecommunication network having time orthogonal wideband and narrowband systems

Abstract: A telecommunications network including a CDMA system and FDMA/TDMA system, both operating in a common frequency range, is disclosed. In an embodiment of the invention, the transmission and reception of narrowband FDMA/TDMA signals on a plurality of radio frequency channels within FDMA/TDMA system is synchronized such that at least one time slot (300) of each TDMA frame (310) on each radio channel is reserved. The transmission and reception of CDMA signals in the CDMA system is then performed during the reserved time slots of each TDMA frame. In an alternative embodiment, complete TDMA frames (310) on each radio channel are reserved for CDMA transmission and reception.

Channel allocation method for a packet network

Abstract: A method for allocating a data transmission channel/sub-channel in a telecommunication network. A network includes a telecommunication controller (BTS) and several terminal equipments (MS). The transmission channel is divided into one or more time slots, each of which comprises one or more sub-channels. One or more time slots or sub-channels can be used as a control channel that is further divided into one or more control sub-channels. The terminal equipments (MS) send data in data packets at least on one sub-channel. The telecommunication controller (BTS) sends to the terminal equipments (MS) information about control sub-channels and their allocation situation. Different priorities (P1 to P4) are assigned to the data packets to be sent and to the control sub-channels. On the basis of the priority of the data packet to be sent and the priority of the control sub-channels, each terminal equipment (MS) determines the moments when it may send a channel request.

Wireless communication system with dynamic channel allocation

Abstract: A plurality of base stations communicate with a plurality of mobile units. Each base station includes a base station transceiver that receives inbound information from the mobile units and transmits outbound information to the mobile units. A mobile switching center (MSC) is coupled to the base stations and communicates the inbound information and outbound information with the base stations. The base stations each include signal detectors that detect signal strength of the inbound information, co-channel information and adjacent channel information. The MSC maintains a table of signal strength per communication channel and allocates communication channels to the base stations based on the signal strength information. The inventive dynamic channel allocation includes several channel allocation algorithms that can be active at the same time. Only one of the algorithms is active at a time. The choice of the algorithm is based on current interference conditions and traffic load. The invention is implemented in the MSC and base stations of a digital cellular network using wideband technology for its air interface.

Adaptive antenna transmission for frequency duplex digital wireless communication

Abstract: Methods are reported for adaptive phased array transmission of digital wireless communication signals for the purpose of improving network call capacity. Frequency division duplex (FDD), time division multiple access (TDMA) communication channels are considered. The proposed techniques are designed for severe multipath environments with large Doppler, angle and delay spreads. No knowledge of array geometry, propagation path angles or portable feedback is required to adapt the transmission weight vectors. The time or frequency averaged spatial covariance of the received reverse link signal vector is decomposed into desired signal and interference subspaces which are used to form quadratic optimization problems involving matched filter bound cost functions. A dynamic channel allocation algorithm searches for frequency channels in which the adjacent cell portables are spatially compatible with the desired portable. Results of cellular network simulations are provided to illustrate the network call capacity improvements that are possible with the proposed FDD transmission approach.

Fast broadcasting for hot video access

Abstract: Using multiple channels to broadcast a popular video can reduce the viewer's waiting time. With the same bandwidth allocation as conventional broadcasting schemes, pyramid broadcasting schemes can provide users with shorter waiting time. This paper presents a new broadcasting method, which can reduce the user's waiting time much greater than previous schemes. With the same waiting requirement for a popular movie, the new algorithm needs much less bandwidth and, thus, greatly saves the bandwidth requirements. At the client end, the buffer requirement is in between previous pyramid schemes. However, using the new scheme, if a set-top box has no buffer, its user can still have the movie with longer waiting time, but previous pyramid schemes cannot provide continuous video service without buffer.

Method and arrangement for channel allocation in a radio communications system

Abstract: The present invention relates to a method and an arrangement for channel allocation in a radio communication system in which data is transmitted between two stations over two or more radio channels (SPDCH3-SPDCH7). Data is communicated as packets which are divided into blocks (b1-bm) while the transmission follows a protocol for automatic re-transmission of data that have been erroneously transmitted. In accordance with the proposed method, channels for re-transmission (SPDCH5, SPDCH6) are allocated with respect to a transmission parameter (TP), which has been created at a previous transmission and which is based upon information of the result (Nack) of said previous transmission. The transmission parameter (TP) is aimed to ensure that re-transmission is performed via those channels (SPDCH5, SPDCH6) which have the highest probability of transmitting data correctly. The channels (SPDCG5, SPDCH6) which had the highest transmission quality in said previous transmission are expected to have the highest transmission quality also by re-transmission.

Simulation results of the capacity of cellular systems

Abstract: We study the capacity of cellular systems with interference-adaptation dynamic channel allocation (DCA) through a set of heuristics that evaluate the required number of channels for some mobile traffic pattern. In particular, we evaluate the improvement in the reuse factor given the knowledge of the mobiles' locations. Assuming that the mobiles' locations are sampled from the uniform random distribution or are fixed on a uniform grid, we show the effect of a number of parameters, such as the number of mobiles per cell, the minimum allowable signal-to-interference ratio, and the limited knowledge of mobiles' locations. We also investigate the effect of shadow fading and signal-based power control. Although previous papers have proposed various heuristics with varying performance, we present heuristics that are shown to give the maximum packing results based on our assumptions. In particular, the single-interferer assumption, used throughout our work, is justified and the optimality of the square-root signal-based power control is proven.

Exploiting the temporal structure of MPEG video for the reduction of bandwidth requirements

Abstract: We present a novel bandwidth allocation scheme for transporting variable-bit-rate MPEG traffic from a video server. Using time-varying envelopes to characterize the traffic, this scheme achieves significant bandwidth gain, via statistical multiplexing, while supporting stringent, deterministic QoS guarantees. The gain can be maximized by allowing the server to appropriately schedule the starting times of video sources, at the expense of some negligible startup delay. For homogeneous streams, we give the optimal schedule that results in the minimum allocated bandwidth. A suboptimal schedule is given in the heterogeneous case, which is shown to be asymptotically optimal. Efficient online procedures for bandwidth computation are provided. Numerical examples based on traces of MPEG-coded movies are used to demonstrate the benefits of our allocation strategy.

Adaptive channel allocation system for communication network

Abstract: An adaptive channel allocation system is provided which monitors the actual channel bandwidth used by network sources Sources which have placed demands for network bandwidth, but not used that bandwidth, have their channel resources down-allocated according to a smoothed exponential function Sources which are idle are detected by means of an aging function

Dynamic channel allocation

Abstract: According to the invention, a pilot signal (4) is transmitted from a base station on each available carrier. This is done for each available carrier and in every time slot of the carrier irrespective of whether or not a useful signal is transmitted in the time slot. The pilot signal contains a limited quantity of information concerning the base station, such as information about the radio interface. The information is time slot synchronized so that the same information is transmitted in every time slot. The pilot signal level varies, and in time slots which are in traffic use it is suitably lower than the level of the useful signal (1) proper, but in idle time slots it has a very low static level. It has the same band width Df as the normal useful signal. However, it is coded in a different way than the useful signal and in such a way that although it almost drowns in noise, it can still be extracted from the noise. The mobile gets information from the pilot signal on the state of channels (time slots) in the uplink direction. When deciding to perform channel exchange, it chooses any free channel it likes and transmits an access burst to the base station on this channel. If the base station accepts the channel, it will transmit back an access grant burst on the same channel, whereafter the base station and the mobile will immediately transfer the traffic to this channel.

Method and apparatus for dynamic channel allocation for wireless communications using channel occupancy data

Abstract: The present invention concerns the efficient use of the radio spectrum in wireless communications. Channel occupancy data and channel availability data concerning a specific base station and its neighbors are used to assign frequency channels to mobile units and/or base stations. The channel occupancy and availability data may be located at a base station or at a mobile switching center. Channels are preferably assigned as channel pairs.

An efficient priority-based dynamic channel allocation strategy for mobile cellular networks

Abstract: Priority-based dynamic carrier allocation strategies can be classified into three categories: static-priority, dynamic-priority, and hybrid-priority strategies. Strategies based on static priorities do not consider the local carrier reuse conditions, while dynamic-priority strategies do take these conditions into consideration. Intuitively, one would expect dynamic-priority strategies to perform better than static- and hybrid-priority strategies, but in the literature it is the other way around-existing dynamic-priority strategies are out-performed by some static- and hybrid-priority strategies. We propose a dynamic-priority strategy which is a significant improvement over all existing strategies. Under various traffic conditions, our simulation results indicated that the proposed strategy could reduce the call blocking/failure rate by a margin ranging from 15% to 95%.

Channel allocation method and radio system using a combination of tdma and cdma

Abstract: The invention relates to a radio system and a channel allocation method in a radio system comprising at least one base station (300) communicating with terminals (308 to 314) within its coverage area (304), and in which method air interface resources are allocated to different terminals with a combined time and code multiple access method in such a way that the signal of one or more terminals is transmitted in each time slot (TS0 to TS6). In order for air interface resources to be efficiently allocated to different connections, in the method of the invention terminal signals (308 to 314) are grouped into different time slots on the basis of the connection characteristics of each terminal.

Radio communication system and method for avoiding control channel interference

Abstract: A radio communication system including a plurality of base stations which communicate with a plurality of radio terminals respectively is provided with a capability of avoiding occurrence of radio interference of control channel signals among a plurality of base stations even when a plurality of the base stations are located in the close vicinity of each other. The base station of the radio communication system is provided with a device for receiving, when the power is turned on, a control channel signal which is being transmitted at a certain interval by each of the other base stations in the system, a device for frame synchronizing each of TDMA frames of the control channel signal which is received, a device for extracting base station identification information of each of the other base stations from the TDMA frames which are frame synchronized, and a device for storing in a memory each of the base station identification information which is extracted. The base station further includes a device for determining a cycle of transmitting a superframe signal in accordance with the number of the other base stations using the control channel in the system, which is determined based upon the base station identification information stored in the memory.

Long term resource allocation in video delivery systems

Abstract: In typical video delivery systems offering programs on-demand, service should be be nearly immediate and continuous. A video server can provide this type of service by reserving sufficient network and server resources for the duration of playout. Scalability and reduced cost can be achieved using a single channel to serve multiple customers waiting for the same program (referred to as batching). Batching is especially useful during high load periods typically occuring during evening prime time hours. Typical channel allocation algorithms use a greedy, allocate-as-needed policy. Variations in system load can cause these algorithms to suffer poor and unpredictable short-term performance, and non-optimal long term performance. In this paper, we develop a set of realistic workloads, identify the limitations of greedy allocation algorithms, and propose a set of rate-based allocation schemes to solve these limitations. The performance of various video delivery systems are simulated and compared. The rate-based policies are shown to be robust for the workloads examined, and are easy to implement.

Renegotiated CBR transmission in interactive video-on-demand system

Abstract: An interactive video-on-demand (IVOD) system requires transmission bandwidth allocation for each user. Since the volume of data in each video frame is variable, dynamic bandwidth allocation is desirable. In this paper, a new scheme that dynamically determines required bandwidth based on the queue length at the viewer's set-top box (STB) is proposed. Although this method is in the renegotiated CBR (constant bit rate) category, it requires no precalculation, so it is easily applied to IVOD. The variance of the video transmission rate for each user is an important factor as it affects the service quality of other multiplexed traffic. It is desirable that the transmission rate is changed gradually. A multi-layer concept is introduced to achieve this. Through numerical evaluation using actual movie data, we demonstrate that the variance of the transmission rate is close to the optimal value and the bandwidth utilization is close to unity.

Modeling resource management in cellular systems using Petri nets

Abstract: Modeling and analysis tools are essential for the design and evaluation of complex systems. This is particularly true for cellular systems, where, for instance, a variety of handoff, channel allocation, and data-transmission algorithms have been proposed. The capabilities of Petri nets (PNs) are used as a novel approach in the analysis of handoff, dynamic channel allocation (DCA), and cellular digital packet data resource management problems. The generalized stochastic PN (GSPN) models are obtained and analyzed as continuous-time Markov chains (MCs) derived from the reachability graphs. Solution of the MC results in performance indicators, which show the impacts of different algorithms on the system behavior.

Channel allocation methods for data dissemination in mobile computing environments

Abstract: We discuss several channel allocation methods for data dissemination in mobile computing systems. We suggest that the broadcast and on-demand channels have different access performance under different system parameters and that a mobile cell should use a combination of both to obtain optimal access time for a given workload and system parameters. We study the data access efficiency of three channel configurations: all channels are used as on-demand channels (exclusive on-demand); all channels are used for broadcast (exclusive broadcast); and some channels are on-demand channels and some are broadcast channels (hybrid). Simulations on obtaining the optimal channel allocation for lightly-loaded, medium-loaded, and heavy-loaded conditions is conducted and the result shows that an optimal channel allocation significantly improves the system performance.

Transmission device and system having the same

Abstract: A transmission device includes a channel allocation part which groups channels defined on a transmission line into groups and allocate, for each of the groups, the channels in one of predetermined transmission modes which can be defined on a dual link formation of a network to which the transmission device can be connected.

Transmission/reception method based on frequency division multiple access having changeable communication channel bandwidths and communication apparatus employing the method

Abstract: An FDMA (Frequency-Division Multiple Access) transmitter-receiver for use in an FDMA communication system which is capable of changing a bandwidth of a channel as required. The FDMA transmitter-receiver includes: a plurality of trans-demultiplexers which are different in the number of channel multiplexings from each other and each of which serves to convert the received FDMA signal into a TDMA signal; a communication signal demultiplexing/multiplexing circuit for subjecting the output communication channel signals from the trans-demultiplexers to demultiplex and channel-reassignable multiplex them; a plurality of trans-multiplexers which are provided in correspondence to the plurality of trans-demultiplexers and each of which serves to convert the output channel signal after demultiplexing and remultiplexing from the associated communication signal demultiplexing/multiplexing circuit into an FDMA signal; an adder for adding the FDMA signals outputted from the trans-multiplexers; and a transmission circuit connected to an output of the adder for transmitting therefrom the signal which has been obtained by adding the FDMA signals. The bandwidth per channel of each of the trans-demultiplexers and the trans-multiplexers is different in correspondence to the number of channel multiplexing.