Showing papers on "Channel allocation schemes published in 1991"

Equivalent capacity and its application to bandwidth allocation in high-speed networks

Abstract: The authors propose a computationally simple approximate expression for the equivalent capacity or bandwidth requirement of both individual and multiplexed connections, based on their statistical characteristics and the desired grade-of-service (GOS). The purpose of such an expression is to provide a unified metric to represent the effective bandwidth used by connections and the corresponding effective load of network links. These link metrics can then be used for efficient bandwidth management, routing, and call control procedures aimed at optimizing network usage. While the methodology proposed can provide an exact approach to the computation of the equivalent capacity, the associated complexity makes it infeasible for real-time network traffic control applications. Hence, an approximation is required. The validity of the approximation developed is verified by comparison to both exact computations and simulation results. >

Method and apparatus for dynamic channel bandwidth allocation among multiple parallel video coders

Abstract: A dynamic channel allocation unit (103) specifies a bit rate for each video coder in a set of parallel video coders (102-1,102-N) comprising an overall video coder The dynamic channel allocation unit is supplied from each individual video coder with an average frame quantization step size for the previous frame and the average number of bits produced per pel For the current image frame the dynamic channel allocation unit computes a set of channel sharing factors, ie, the percentage of the total channel bandwidth to be allocated to a particular video coder One channel sharing factor is computed for each individual video coder Individual members of the set of channel sharing factors may be further refined to reflect the prior history of the channel sharing factor for their corresponding coder Additionally, the set of estimates may be normalized to reflect the actual number of bits that can actually be produced by each individual video coder

Improved call set-up and spectrum sharing in radio communication on systems with dynamic channel allocation

Abstract: The call set-up technique of this invention is characterized by the use of channel information from both base station and subscriber terminal in determining the radio traffic channel upon which to set-up a new call. Communication between the base station and subscriber terminal is carried out on a signalling channel until the traffic channel is chosen. Calls are set-up so that they proceed on the radio channel which, of a set of channels under consideration by the subscriber terminal, contains the least amount of interference as measured at the subscriber terminal. The set of channels under consideration by the subscriber terminal is a subset of the entire set of channels allocated to the service. This subset is comprised of those channels having little interference, as measured by the base station, and which, additionally, are not reserved exclusively for stationary, fixed-allocation services in the geographic location of the base station. The call set-up technique thereby assures that calls proceed on channels containing little interference from the viewpoint of both base station and subscriber terminal. The technique also facilitates sharing of the radio spectrum with stationary, fixed-allocation services because there is no need to program each subscriber terminal to avoid the spectrum allocated to the fixed service.

Performance analysis of cellular networks

Abstract: Dynamic channel allocation can reduce the probability of blocking in cellular telephone networks. However, more is needed to achieve optimal performance. The author aims at estimating the minimal blocking probability for some simple cellular networks. Some dynamic channel allocation strategies are analyzed, the optimal performance (obtained by dynamic allocation and flow control) of some very simple networks is computed, and simple bounds on optimal performance are presented. These results lead to a better understanding of cellular networks and can be used to evaluate new control algorithms. >

Capacity of digital cellular TDMA systems

Abstract: The capacity of digital TDMA (time-division multiple-access) systems is addressed. It is projected that capacity improvement will be of the order of 5-10 times that of analog FM without adding any cell sites. For example, the North American TIA (Telecommunication Industry Association) standard offers around 50 Erlang/km/sup 2/ with a 3-km site-to-site distance. In addition, the TDMA principle allows a faster handoff mechanism (mobile assisted handoff), which makes it easier to introduce microcells with a cell radius of about 200 m. This gives substantial additional capacity gain beyond the 5-10 factor given above. TDMA makes it possible to introduce adaptive channel allocation (ACA) methods. ACA is a mechanism that provides efficient microcellular capacity. ACA also eliminates the need to plan frequencies for cells. It is concluded that the air-interface of digital TDMA cellular may be used to build personal communication networks. >

Dynamic channel allocation method

Abstract: A dynamic frequency allocation method of a digital, mobile, portable telephone system wherein in communications between a plurality of base stations which are connected to a public telephone network and/or a private branch exchange and which respectively generate synchronization in an independent manner and mobile stations receiving service therefrom, each base station uses a communication signal transmission channel including a frequency and a time slot pair respectively selected from a plurality of frequencies and a plurality of time slots related thereto to implement a multichannel time division multiplex/time division duplex communication. Each of the base and mobile stations receives a communication signal of a different station communicating with synchronization independent of the pertinent station by use of a different time slot at the same frequency of the channel used by the station to receive a communication sent thereto so as to measure an interval or a distance between the time slot used by the different station and the time slot assigned thereto. Based on the measurement result, a chance of a collision between these two time slots is estimated such that depending on the estimation result, the pertinent station detects free channels not being used by any other stations to conduct a channel transition to one of the detected free channels.

The nonuniform compact pattern allocation algorithm cellular mobile systems

Abstract: An algorithm for allocating nominal channels according to traffic distribution is designed. The algorithm attempts to minimize the average blocking probability as nominal channels are allocated one at a time. Simulation results show that the system's traffic-carrying capacity can be increased by about 10% by the use of this algorithm, and that the gain is additional to the improvement obtained from the channel-borrowing strategies. If the effect of shadow blocking is considered in the assignment of channels, only a very small increase in the traffic capacity is observed. >

Intra-cell call hand-over in radio communication systems with dynamic channel allocation

Abstract: The intra-cell call hand-over technique of this invention is characterized by the use of channel information from both base station and subscriber terminal in determining a standby radio traffic channel upon which to hand over a call. Communication between the base station and subscriber terminal is carried out on an inband or associated signalling channel for the selection of the standby traffic channel. The standby radio channel is the channel, which, of a set of channels under consideration by the subscriber terminal, contains the least amount of interference as measured at the subscriber terminal. The set of channels under consideration by the subscriber terminal is a subset of the entire set of channels allocated to the service. This subset is comprised of those channels having little interference as measured by the base station. The call hand-over technique thereby assures that calls proceed on channels containing little interference from the viewpoints of both base station and subscriber terminal.

An analysis of statistical multiplexing in an ATM transport network

Abstract: The traffic characteristics of an asynchronous transfer mode (ATM) network are analyzed by theoretical methods. A new method is proposed to express the burstiness of the cell arrival process. Both statistical multiplexing and statistical bandwidth allocation are quantitatively evaluated. When packetized video traffic and voice traffic are multiplexed, the number of multiplexable sources strongly depends on the peak bit rate of the multiplexed video sources, and statistical bandwidth allocation is ineffective without control. On the other hand, lowering the peak bit rate of video traffic effectively improves bandwidth utilization. >

A method and apparatus for enhancing signalling reliability in a cellular mobile radio telephone system

Abstract: A method and apparatus for achieving reliable transmission of signalling messages in a cellular system in which the frequency plan, frequency/time slot allocation plan, code channel allocation plan, or dynamic/adaptive channel allocation rule of the system is violated by allowing adjacent base stations to reuse particular frequencies/time slots/channels for signalling a particular mobile station. In situations where signalling messages, such as handoff commands, which are communicated between a base station and a mobile station are not properly received by the mobile station, an alternate communications channel will be established to ensure the reception of these messages. The alternate channel is provided by repeating the message through a channel associated with a base station which has better radio characteristics. The channel selected for transmission of the message by the new base station will be on the same frequency/time slot/code as used by the established connection.

Performance of dynamic channel allocation in the DECT system

Abstract: The authors present the results of computer simulations of an indoor wireless PABX system conforming to the Digital European Cordless Telecommunications (DECT) standard. Of particular interest is the evaluation of the dynamic channel allocation algorithm proposed by the DECT standard. It is shown that this system is capable of meeting the expected capacity requirements for high-density indoor applications as long as there are a sufficient number of base stations on each floor of the building. System performance has been measured in terms of setup blocking, handover blocking, lost calls, cleared traffic, and carrier-to-interference ratios. >

Method for managing radio communication resources

Abstract: In a communication system (100) that performs radio channel management, there is a method and and apparatus for reducing contention and superfluous channel allocation between a plurality of mobile units (101,102 and 103), making multiple requests. In this effort, upon receipt of an access request (at 210 or 510) and after a determination that communication resources are available (at 530-570), the system determines an access request count (at 310) for each received access request. Thereafter, the system is responsible for altering system resources (at 360 or 370) as a function of the access request count in order to reduce the likelihood of contention. In addition, the system (100) is designed to determine a system processing delay (at 610) for each received access request and thereafter adjust a range of mobile unit retry intervals ((at 645 or 655) as a function of the processing delay, whereby the likelihood of more than one channel being assigned to a unit making multiple requests is reduced.

The bandwidth allocation of ATM through genetic algorithm

Abstract: The authors develop an optimization algorithm based on the genetic algorithm to achieve the bandwidth allocation of the ATM (asynchronous transfer mode) network. Using the ATM technique, one can flexibly reconfigure the network and reassign the bandwidth to meet the requirements of all types of services. By dynamically routing the traffic and adjusting the bandwidth assignment, the average packet delay of the whole network can be reduced to a minimum. The M/M/1 queueing model can be used to analyze the performance. The genetic algorithm is applied to the bandwidth allocation problem of ATM to find the minimum average packet delay of the network. Simulation results show that a delay improvement (41.8%) can be achieved within 30 iterations. >

Graph theoretical considerations of channel offset systems in a cellular mobile system

Abstract: The problem of assigning channels in a channel-offset-type of cellular mobile radio communication system is formulated as a problem of assigning channels to the vertices of a network. It is shown that the assignment problem in a network is a generalized graph coloring problem. When the interchannel interference function is a rational number, the optimal channel offset scheme is obtained. and upper and lower bounds of the minimum total bandwidth in a channel-offset scheme are derived. These factors give basic and useful knowledge for designing a channel-offset system of a cellular mobile system, and they are useful not only for a fixed channel assignment but also for a dynamic channel assignment and rearrangement. >

Multiple channel architecture: a new optical interconnection strategy for massively parallel computers

Abstract: A parallel processing architecture based on multiple channel optical communication is described and compared with existing interconnection strategies for parallel computers. The proposed multiple channel architecture (MCA) provides a large number of independent, selectable channels (or virtual buses) using a single optical fiber. Arbitrary interconnection patterns and machine partitions can be emulated via appropriate channel assignments. Hierarchies of parallel architectures and simultaneous execution of parallel tasks are also possible. The authors describe previous attempts in processor, memory, and input/output device interconnection, a basic overview of the proposed architecture, various channel allocation strategies that can be utilized by the MCA, and a summary of advantages of the MCA compared with traditional interconnection techniques. >

Photonic multihop bus networks

Abstract: The photonic bus network (PBNet) approach to the design of small backbone networks is considered. The basic building block of PBNets consist of a linear multihop network interconnected in a bidirectional bus virtual topology using point-to-point optical channels. The system is designed to exploit transmissive optical star technology employing multichannel coherent lightwave modulation, but a wavelength-division implementation is also possible. The NCounter Protocol is introduced as a way of achieving fair bandwidth allocation in the presence of network overload conditions. Due to the optical implementation, there is considerable flexibility in PBNet topological design and bandwidth deployment. New design algorithms are introduced for this purpose. Performance results show that substantial improvements in system operation are possible using the proposed design techniques. In addition, the concept of receiver allocation is introduced which permits simple performance evolution of fixed-channel PBNets. >

A fixed channel assignment algorithm for three-dimensional frequency reuse environment

Abstract: An algorithm for channel assignment in the three-dimensional cellular reuse environment is reported. The algorithm is capable of estimating the number of channel sets required to serve a cubic cellular configuration, taking the co-channel and adjacent channel constraints into consideration. The package also estimates the capacity of the system under various co-channel separation conditions and channel grouping strategies. It can be used for 3D office or residential buildings of various sizes. The developed algorithm is suitable for operation in FDMA (frequency division multiple access) and TDMA (time division multiple access) based cellular systems. It is also applicable for channel assignment in two-dimensional frequency reuse environments. Computer simulations were performed employing the channel assignment algorithm under a diversified set of conditions. Results indicate that system capacity is highly sensitive to the uniformity of traffic distribution and to the number of channel sets. >

Regular cellular reuse patterns

Abstract: The author attempts to define what regular cell reuse patterns are in the case of omnidirectional hexagonal cells and shows that there are more such patterns than the ones usually presented; for instance, patterns of 5 or 11 cells are possible. An exhaustive presentation of the reuse patterns satisfying the definition is given. Some rough performance evaluations are included, giving some ideas of the C/I (carrier to interference ratio) protection with a simple propagation model. Some related problems are addressed, such as the application to frequency hopping and the problem of how to allocate frequencies in order to limit adjacent frequency interferences. >

Optimum Global Transmitter Power Control in Cellular Radio Systems

Abstract: Transmitter power control as a method to reduce cochannel interference for a given channel allocation is investigated. The performance is analyzed in terms of interference. (outage) probabilities. Qpthm and nearoptimum global power control schemes are proposed. Using these schemes upper bounds on the performance of power control schemes are derived. Numerical results indicate that these upper bounds exceed the performance of conventional systems by an order of magnitude in interference suppression and by a factor of 5 in capacity. The structure of the optimum algorithm shows that efficient power control and dynamic channel assignment algorithms should be closely related.

Adaptive access control of multiple traffic classes in ATM networks

Abstract: An admission control and bandwidth allocation strategy is applied to several traffic classes entering an ATM (asynchronous transfer mode) network through a statistical multiplexer. At the call level, incoming virtual calls are either accepted or refused on the basis of a class-selective control rule designed to maintain a certain grade of service. Each class is assigned a buffer partition and a virtual capacity share, which affect the parameters of the acceptance controller. Buffer space is assigned statistically with an offline procedure; on the other hand, bandwidth shares are periodically recomputed online at the cell level, by means of the (parametric) constrained minimization of a cost function, which takes cell loss probability and refused traffic into account. These quantities are computed by observing the number of refused, accepted, and active (i.e. possibly generating bursts) calls within the previous decision interval, and are assumed to be slowly varying with respect to the cell dynamics. In turn, the results of the optimization are used to adaptively adjust the parameters of the access controller. >

A model for dynamic channel allocation in an ISDN

Abstract: The authors propose a dynamic channel allocation strategy in an integrated services digital network (ISDN) based on traffic characteristics and channel utilization. Conventional channel allocation schemes such as complete sharing channel allocation, complete allocation, and moving boundary channel allocation are examined and compared with the proposed dynamic channel allocation scheme. An analytic model is developed and a solution based on the moment-generating functional technique is given. Numerical examples are also presented. The result shows that the scheme improves the system performance. >

Adaptive multiplexing system

Abstract: PURPOSE:To quicken bit rate assignment to each channel and to improve the degree of freedom of assignment in response to the quantity of coded information production quantity when picture signals of plural channels are subject to inter-frame coding and time division muitiplex. CONSTITUTION:Data B1 or B4 representing quantity or increase/decrease of coded information quantity in coding sections 1-1-1-4 of plural channels is given to a control section 3 and the channel allocation to a sub frame part in a multiplexed data Dm is set accordingly. In response to the result of channel allocation, an adaptive multiplexer section 2 applies time division multiplex to coded data D1-D4 of each channel, codes and adds data E being the result of channel allocation to form the multiplex data Dm and the data are sent. A receiver side decodes the data E from the code in the multiplex data Dm to obtain an allocation timing of the coded data D1-D4 of each channel in the multiplex data Dm thereby demultiplexing and decoding each channel.

Dynamic channel assignment for cellular mobile radio system using feedforward neural networks

Abstract: Conventional dynamic channel assignment schemes are both time-consuming and algorithmically complex An alternative approach using a multilayered feedforward neural network model is examined The results of the neural network approach are compared with those of a maximum packing strategy technique The comparison shows that the neural networks approach is well-suited to the dynamic channel allocation problem >

Performance analysis of index-vector-based algorithms for fast adaptive channel allocation in cellular networks

Abstract: Two algorithms for fast adaptive channel allocation are proposed. Both algorithms are based on a logic structure called the index vector. The first algorithm uses the main index vector only. The second algorithm uses a hierarchically organized index vector, which consists of the main and an auxiliary index vector. The main advantage of the algorithms is a very fast determination of an available channel when there is a request for a call initialization or a hand-off. Also, they permit almost immediate call rejection if the call cannot be supported for any reason. >

CDMA and Spread Spectrum Techniques Versus FDMA and TDMA in Cellular Mobile Radio Applications

Abstract: In cellular mobile radio a changeable number K of users has to be accommodated. Each of the K different users may access an M-ary symbol alphabet. Therefore, some sort of multiple access principle must be implemented. To date, in the second generation mobile telecommunication system (GSM) FDMA and TDMA are used. CDMA and spread spectrum techniques are ideal means to combat time-variant multipath channels. There are further advantages over FDMA and TDMA like graceful degradation and reduced timing organization as well as the possibility of position location. With respect to a novel coherent multiple transmission (CMT) and reception (CMR) scheme a considerable gain can be achieved when using CDMA and spread spectrum and at the same time the carrier-to-interference ratio will be noticeably reduced. In this paper we shall emphasize the potential of CDMA and spread spectrum techniques in an illustrative way without going into technical details.

Combined channel allocation and routing algorithms

Abstract: Joint optimization of capacity and flow assignment (CFA) is considered for high-speed packet-switched networks in which multiple trunk links are modeled by parallel M/M/1 queues. A quadratic cost function is considered to reflect both switching and line costs. Queuing, transmission, nodal processing, and propagation delays are all incorporated into the optimization problem. The proposed CFA problem is shown to be a convex optimization problem, thus ensuring a global solution. By invoking optimality of the CFA problem and relaxing the integral channel constraint to a continuous variable, a set of nonlinear equations is derived for the optimal solutions. To circumvent the computational burden involved with the continuous solution approach and to capture the discrete nature of channel allocation, an efficient discrete optimization algorithm is developed based on a marginal analysis approach. >

A frame-based DQDB protocol for consecutive slots transmission in Gbit/s metropolitan area networks

Abstract: A frame-based distributed-queue dual-bus (FB-DQDB) medium access protocol is proposed for Gb/s networks. By dividing the slots into fixed-size frames and delaying a channel access until the beginning of the next frame, each station can transmit a number of consecutive slots up to the limit of a frame size. It therefore reduces the packet reassembly processing overhead and the number of receiving buffers required. By allowing each station to make multiple requests on the request channel and with one request per frame, the FB-DQDB protocol can give a maximum throughput and fair bandwidth allocation among the stations over a wide range of cable lengths. It gives a throughput close to 1 with fixed-size messages and its throughput is lower with variable-size messages. >

Performance evaluation of a UMTS in a urban environment

Abstract: By means of a simulation programme comparisons were made between different channel allocation schemes and handover criteria in case of uniformly and nonuniformly distributed traffic. These comparisons were, performed in a typical macrocellular environment. Output parameters included statistical C/I distribution, handover rates and carried traffic. The authors present the main functional and architectural features of the new simulation programme which will allow performance evaluations and comparisons of different spectrum management and channel allocation policies even in a more complex environment such as UMTS (universal mobile telecommunication system) is. >

User oriented satellite networks - Studies on utilization of transmission capacity in TDMA and TDMA/FDMA systems

Abstract: The project to interconnect, in the C.N.R. environment, local area networks via satellite links at high speed, presents the problem of an efficient utilization of the transmit capacity of the satellite channel, as well as problems related to the terminal design. In particular, referring to satellite access schemes in FDMA and/or TDMA, the optimization of the transmission capacity utilization, according to the traffic requirements, is analyzed. Two systems, based on hybrid MF-TDMA, are presented and synchronization problems are analyzed.