Showing papers on "Channel allocation schemes published in 1996"

Channel assignment schemes for cellular mobile telecommunication systems: a comprehensive survey

Abstract: This article provides a detailed discussion of wireless resource and channel allocation schemes. The authors provide a survey of a large number of published papers in the area of fixed, dynamic, and hybrid allocation schemes and compare their trade-offs in terms of complexity and performance. We also investigate these channel allocation schemes based on other factors such as distributed/centralized control and adaptability to traffic conditions. Moreover, we provide a detailed discussion on reuse partitioning schemes, the effect of handoffs, and prioritization schemes. Finally, we discuss other important issues in resource allocation such as overlay cells, frequency planning, and power control.

Adaptive channel allocation in a frequency division multiplexed system

Abstract: A method and system of adaptive channel allocation in a frequency division multiplexed system is provided. In the method and system, a subset of M subcarriers is chosen from a larger set of N subcarriers available for communications on a link. As communications take place on the link, signal quality (C/I) measurements (342) on the subcarriers of the subset of M subcarriers and interference (I) measurements (344) on the subcarriers of the group of N subcarriers are periodically performed. The C/I and I measurements are then used to reconfigure (422) the subset of M subcarriers to reduce co-channel interference on the link.

Apparatus and method for digital data transmission over a CATV system using an ATM transport protocol and SCDMA

Abstract: A method and apparatus for carrying an ATM communication protocol on a hybrid fiber coax CATV system. Point to point communication is supported by use of synchronous code division multiplexing on the physical and by assigning on the MAC layer one or more orthogonal SCDMA codes exclusively for use by pairs of devices needing to communicate such the head end and any customer premises equipment. Quality of service or guaranteed bandwidth availability is implemented by controlling the code space at the MAC layer such that certain CPEs having in use peripherals which cannot tolerate interruptions in data flow may reserve one or more SCDMA codes for use exclusively by them. Standard ATM cells are modified by the addition of a two byte virtual link header which identifies to which CPE a particular ATM packet is destined. This virtual header also makes possible broadcast and multicast of packets from the head end to all CPEs. Each byte in each ATM cell has 8 bits of data and a 9th bit which is encoded with to indicate where the ATM cell starts and includes CRC data for error detection and correction. Bandwidth is allocated by the head end computer which executes algorithms on the MAC layer to collect actual bandwidth usage information and requests for bandwidth and prioritize them in accordance with the channel allocation/reservation scheme currently use. The channel allocation/reservation scheme can be changed on the fly and reallocation calculations to adjust bandwidth allocations are calculated every 10 milliseconds and the new allocations are distributed in downstream messages which are transmitted to all CPEs.

Reinforcement Learning for Dynamic Channel Allocation in Cellular Telephone Systems

Abstract: In cellular telephone systems, an important problem is to dynamically allocate the communication resource (channels) so as to maximize service in a stochastic caller environment. This problem is naturally formulated as a dynamic programming problem and we use a reinforcement learning (RL) method to find dynamic channel allocation policies that are better than previous heuristic solutions. The policies obtained perform well for a broad variety of call traffic patterns. We present results on a large cellular system with approximately 4949 states.

Adaptive-Dynamic channel assignment organization system and method

Abstract: A channel assignment system allocates channels to various cells by the optimal partitioning of the available radio frequencies into non-overlapping sets, the optimal grouping of co-user cells, and the best allocation of the former to the latter. Maximization of traffic handling capacity is, for one embodiment, expressed as the maximization of a bottleneck capacity ratio, known as the capacity factor. The capacity ratio for a cell is defined as the ratio of the number of radio frequencies allocated to the cell over the number of radio frequencies needed to meet blocking probability requirements. Given a channel allocation, the latter is fixed once the traffic loads and desired blocking are specified. The solution to attain an optimal non-regular channel assignment is decomposed into two mathematical programs designated a Master Program and a Subprogram. These are solved iteratively with assistance from a channel set augmentation technique implemented between solutions of the Master and Subprogram. A method is also provided for periodic reallocation of channels to cells to address changing capacity requirements in individual cells. A further methodology is provided where a cell, having exhausted its available allocated channels, may "borrow" channels, i.e., it may use channels that are not allocated to the cell.

Subspace based estimation of the signal to interference ratio for CDMA cellular systems

Abstract: The signal-to-interference ratio (SIR) has been highlighted in the literature to be a most efficient criterion for several methods aiming at reducing the effects of cochannel interference, e.g. diversity reception, dynamic channel allocation and power control. In this paper we address the problem on how to obtain fast and accurate measurements of this parameter in a practical context. We develop a general SIR estimation technique for narrow-band cellular systems, that is based on a signal subspace approach using the sample covariance matrix of the received signal. Simulation results for a GSM-like system show that the SIR can be estimated to within an error of 0.3 dB after only 200 ms, or within an error of 0.1 dB after only 0.6 seconds.

A dynamic channel allocation technique based on Hopfield neural networks

Abstract: The interest in global spectrum allocation techniques is growing with the always increasing spectrum demand for (cellular) mobile communications. However, the best algorithms suffer from high computational times that reduce the possibility of a practical implementation. This paper deals with a dynamic channel allocation (DCA) technique based on an energy function whose minimization gives the optimal allocation. Due to the particular formulation of such an energy function, the minimization can be performed by a Hopfield neural network for which a fast hardware implementation has been recently proposed in the literature. The performance of the proposed DCA technique is derived by computer simulations. Comparisons with a classical fixed allocation technique (FCA) and a different DCA technique are shown to highlight the better performance of the proposed DCA technique.

PRMA/DA: a new media access control protocol for wireless ATM

Abstract: We propose a media access control (MAC) protocol for wireless local area networks (LANs) that is capable of supporting various types of traffic demands, such as constant bit rate (CBR) voice, variable bit-rate (VBR) video, and packet data. In addition, the proposed protocol provides a seamless connectivity to a broadband ATM backbone network. Our protocol, having an air interface comparable to ATM, adopts a dynamic channel allocation scheme which enables expeditious network-access and utilizes bandwidth resource efficiently. The simulation results presented show the improvements of dynamic channel allocation over the static channel allocation scheme in terms of key performance metrics such as: throughput, call blocking probability, network access delay and cell transmission delay.

Performance of an OFDM-TDMA mobile communication system

Abstract: The multicarrier transmission technique (OFDM) is considered in combination with a TDMA/TDD multiple access scheme for a cellular mobile communication system. Performance analysis is presented for the uncoded and coded (TCM) case. It is shown that OFDM systems have a large potential concerning the flexible allocation of the total given bandwidth to different users. This flexibility can be exploited to adapt to the impairments of the radio channel, thus increasing the overall performance. Two methods, namely (1) a simple principle to leave out weak subcarriers, and (2) the individual modulation of each subcarrier (adaptive modulation) are studied (for the up-/downlink case in a frequency selective and time-variant radio channel), and results with respect to throughput and BER performance are discussed.

Hybrid access system having channel allocation and prioritized polling schemes

Abstract: An asymmetric network communication system for use in a client-server environment having independent forward and return channels operating at different speeds and/or under different protocols on the same or different communication media to provide efficient utilization of shared resources. A network manager, such as a hybrid access system, effects transmission of packetized data on a forward (downstream) channel from the host server to multiple client devices coupled with a shared downstream media at 10 or more megabits per second while simultaneously providing selectable multiple lower speeds of operation on shared or dedicated return (upstream) channels from the client devices to the host server depending on bandwidth availability, bandwidth demand, service level authorization, etc. for the return channel. Forward and return channels may be located on the same or different communication medium including a CATV network, direct broadcast satellite network, television or radio RF broadcast network, wireless or mobile cellular facilities or the like. The return channel may reside on a PSTN either directly coupled with the host server or connected with the network manager for subsequent transmission to the host server. The network manager handles or controls the forward and return communication to establish interactive full-duplex real-time network sessions between the host and plural client devices. The network manager effects upstream channel allocation in response to channel allocation requests and prioritizes polling wherein the polling cycles or periods differ among respective groups of client devices, depending on their state of operation.

Supporting real time VBR video using dynamic reservation based on linear prediction

Abstract: Variable bit rate (VBR) video traffic is expected to be one of the major applications that need to be supported by broadband packet-switched networks A dynamic bandwidth allocation strategy used to support VBR video traffic is proposed This strategy predicts the bandwidth requirements for future frames using either adaptive or non-adaptive least mean square (LMS) error linear predictors The adaptive technique does not require any prior knowledge of the statistics, nor assumes stationarity Several reservation schemes are also presented Analysis using six one-half hour video traces indicate that prediction errors for the bandwidth required for the next frame are almost white noise By reserving a bandwidth equal to the predicted value, only the prediction errors need to be buffered Because the errors are almost white noise, a small buffer size, high utilization, and a small delay are achieved Simulation results for 1-step linear predictor show that for the same expected cell loss, the buffer size is reduced by more than a factor of 100 and the network utilization is increased by more than 250% as compared to a fixed service rate

Joint source and channel coding for image transmission over lossy packet networks

Abstract: We describe a joint source/channel allocation scheme for transmitting images lossily over block erasure channels such as the Internet. The goal is to reduce image transmission latency. Our subband-level and bitplane-level optimization procedures give rise to an embedded channel coding strategy. Source and channel coding bits are allocated in order to minimize an expected distortion measure. More perceptually important low frequency channels of images are shielded heavily using channel codes; higher frequencies are shielded lightly. The result is a more efficient use of channel codes that can reduce channel coding overhead. This reduction is most pronounced on bursty channels for which the uniform application of channel codes is expensive. We derive optimal source/channel coding tradeoffs for our block erasure channel.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A real time downlink channel allocation scheme for an SDMA mobile radio system

Abstract: In SDMA mobile radio systems where only base stations, but no mobiles are equipped with antenna arrays, co-channel interference on the downlink has to be kept down by beamforming. The performance of the beamformer is determined by the directions of arrival (DOAs) of the users operating in the same frequency/time/code slot. Thus the full capacity of an SDMA cell can only be made use of by an effective channel allocation scheme. In this paper, a real time concept for channel allocation is presented. Furthermore, several criteria to quickly evaluate the spatial separability of subsets of users, were defined and then compared to each other by means of simulations.

Channel allocation for co-located systems based on interferring channel groups

Abstract: A mobile communication system is provided in which a base station commands a mobile station (or field monitor) to measure the field strength for a specific channel. The mobile station reports the measured results to the base station. The measured results are used in conjunction with base station identification codes to obtain a single representative value which is used to determine what channels can be selected and used by the system. This enables an existing cellular system to be utilized as a first mobile communication system, and makes it possible to construct a second mobile communication system in the same area as the service area of the first system.

A network flow framework for online dynamic channel allocation

Abstract: We present a framework based on network flows for dynamic channel allocation. The framework allows us to gracefully extend previously proposed heuristics, while avoiding the problems associated with the optimal packing schemes. The framework is shown to yield parametrizable algorithms that tradeoff the benefit of channel reassignments with the costs. Channel reassignments are allowed to be performed not just at new call arrivals, but also at various other trigger points like call terminations and channel quality deterioration.

Automatic control channel planning in adaptive channel allocation systems

Abstract: Methods and systems for allocating control channels in a radiocommunication system are disclosed. Control channels are each linked to a dedicated traffic channels such that when the dedicated traffic channel is allocated to a particular cell, so is its respective control channel. Implementation according to the present invention is independent of the particular ACA scheme used to determine traffic channel allocation.

Capture division packet access: a new cellular access architecture for future PCNs

Abstract: The authors describe a new cellular access architecture, known as capture-division packet access, which is a packet-oriented architecture able to support the constant bit rate traffic and variable bandwidth on demand necessary for multimedia traffic. The approach integrates the multiple access and channel reuse issues to achieve a high degree of spectral efficiency, and presents general advantages even if used for delay-constrained circuit-oriented traffic. Unlike CDMA and TDMA, wherein the effective data rate of each connection is typically a small fraction of the total radio channel allocated for PCN, the CDPA approach allows each user to access the entire channel, if necessary, for brief periods of time (packet access). Spectrum sharing is accomplished by exploiting the different path losses suffered by the various signals as they appear at the base stations (the capture effect), with co-channel interference abated through time diversity (colliding users do not successively retry in the same time interval). Results suggest that abating co-channel interference by random retransmission may be more effective than spatial isolation at cells using the same channel, as is usual in FDMA-TDMA systems.

Resource management for real-time communication: making theory meet practice

Abstract: This paper focuses on bridging the gap between theory and practice in the management of host CPU and link resources for real-time communication. Using our implementation of real-time channels, a paradigm for real-time communication in packet-switched networks, we illustrate the tradeoff between resource capacity and channel admissibility, which determines the number and type of real-time channels that can be accepted for service and the performance delivered to best-effort traffic. We demonstrate that this tradeoff is affected significantly by the choice of implementation paradigms and the grain at which CPU and link resources are multiplexed amongst active channels. To account for this effect we extend the admission control procedure for real-time channels originally proposed using idealized resource models. Our results show that practical considerations significantly reduce channel admissibility compared to idealized resource models. Further, the optimum choice of multiplexing grain depends on several factors such as resource preemption overheads, the relationship between CPU and link bandwidth, and the interaction between link bandwidth allocation and CPU bandwidth allocation.

Channel management policies for handovers in cellular networks

Abstract: A major criterion in evaluating a cellular system is the handover failure probability — the probability that a mobile call in progress will be forced to abort during a handover because it could not be allocated a radio channel in the new cell. One factor that influences the handover failure probability is the channel allocation policy within each cell. This policy is used to determine how to allocate the limited set of available channels in the cell to two kinds of calls: new calls originating within the cell, and handovers that migrate into the cell from neighboring cells. Two classes of such policies are explored in this paper — nonreserving and reservation-based. Nonreserving policies do not set aside resources for exclusive use by handover calls, whereas reservation-based policies do reserve resources. For the former class, this paper presents an optimal policy and, for the latter, an adaptive traffic-driven reservation policy that improves on static guard channel policies. Analytic and simulation results are provided for policies in each class.

Max-min rate control algorithm for available bit rate service in ATM networks

Abstract: The definition of available bit rate (ABR) service has been a focus of activities of the ATM Forum. The Forum has adopted rate-based schemes as the standard for congestion control of ABR services. The enhanced proportional rate control algorithm (EPRCA) has been suggested as a possible algorithm for the switch behavior. In this paper, we propose a new family of algorithms for the switch behavior, called max-min rate control algorithms (MMRCA). The basic MMRCA scheme uses minimum and maximum rate of all active connections to select which connections should be forced to decrease their rate during congestion; the enhancements of the basic scheme use additional congestion detection mechanisms to prevent potential congestion by intelligently regulating selected connections. The new schemes are fully compatible with the existing ATM standard, and have low hardware complexity. All MMRCA schemes converge to the same fair share for all connections as EPRCA, but achieve faster convergence time; the enhanced MMRCA schemes also require smaller buffer sizes at the switches, and achieve higher link utilization than EPRCA. LANs and WANs are discussed.

PRMA performance in cellular environments with self-adaptive channel allocation strategies

Abstract: The personal communication systems envisaged for next years will have to accommodate a wide range of services with different quality requirements (on delays, bit error rates, etc.), and will often be characterized by a high burstiness (i.e., with relatively short traffic bursts, alternating with comparatively long silence periods). Therefore, an extension of packet communications to the cellular scenario is appealing for its inherent flexibility. The packet reservation multiple access (PRMA) protocol is considered. On the other hand, the current trend in reducing cell sizes poses major planning problems, which cannot be properly coped with by the usual fixed channel allocation methods; therefore, adaptive allocation schemes, which are able to avoid any frequency planning, are currently studied. A review of adaptive channel allocation strategies in view of application to packet switching is carried out. Then, a self-adaptive assignment method (channel segregation) originally developed for circuit switched systems is selected and conveniently adapted for PRMA operations. Simulations show good performance, provided that values of some system variables are correctly chosen.

Worst-case performance of cellular channel assignment policies

Abstract: Many cellular channel assignment policies have been proposed to improve efficiency beyond that resulting from fixed channel allocation The performance of these policies, however, has rarely been compared due to a lack of formal metrics, particularly under nonhomogeneous call distributions In this paper, we introduce two such metrics: the worst-case number of channels required to accommodate all possible configurations of N calls in a cell cluster, and the set of cell states that can be accommodated with M channels We first measure two extreme policies, fixed channel allocation and maximum packing, under these metrics We then prove a new lower bound, under the first metric, on any channel assignment policy Next, we introduce three intermediate channel assignment policies, based on commonly used ideas of channel ordering, hybrid assignment, and partitioning Finally, these policies are used to demonstrate the tradeoff between the performance and the complexity of a channel allocation policy

Advanced planning criteria for cellular systems

Abstract: This article provides a review of the most up-to-date frequency planning techniques suitable for current digital cellular systems. Frequency planning is becoming a key issue in the current scenario, with exceedingly high growth rates in many countries which compel operators to re-configure networks virtually on a monthly basis. Therefore, the search for smart techniques, which may considerably alleviate planning efforts (and associated costs) becomes extremely important for operators in a competitive market. Although reference is made particularly to a market leader (GSM and its offspring), the considerations reported are quite general, and can be applied to any TDMA/FDMA system. The article examines such well-known concepts as fractional loading, frequency hopping, and intelligent antennas in order to elaborate on them and show how they may impact conventional planning methodology and deprive complex dynamic channel allocation methods of any practical interest. The evaluation of this impact is extended to mixed cellular architectures, starting from a real case for the city of Munich and finally identifying some basic guidelines for cell planning.

Bandwidth allocation and routing in virtual path based ATM networks

Abstract: The virtual path (VP) concept in ATM networks simplifies traffic control and resource management. For bandwidth allocation, a VP can carry traffic of the same type (the separated scheme) or of different types (the unified scheme) if the most stringent quality of service (QoS) amongst traffic of different types is used on the VP. In addition, VP capacity is dynamically adjusted in a predetermined incremental size. In this paper, we study a least loaded path-based adaptive routing algorithm called maximum free circuit routing under two bandwidth allocation schemes, in an ATM network employing the VP concept. In particular, we evaluate the call blocking probability and the call set-up processing load with varying bandwidth incremental sizes. It is found numerically how the use of VP trades the blocking probability for call setup processing load. It is also found that the unified scheme could outperform the separated scheme with the use of VP.

Smart antenna backwards compatibility in digital cellular systems

Abstract: This invention teaches a method of operating a cellular communication system, and includes the steps of: (a) allocating mobile stations into groups as a function of their ability to support a smart antenna transmission from a base station; and subsequently allocating frequency channels to the groups of mobile stations in accordance with one of a static allocation and a dynamic channel allocation.

Known and novel diversity approaches as a powerful means to enhance the performance of cellular mobile radio systems

Abstract: The main requirements to be met by third generation mobile radio systems are high cellular spectrum efficiency and high flexibility. The authors focus on high cellular spectrum efficiency, which is difficult to achieve due to the time variance and frequency selectivity of the mobile radio channel and due to interference. It is known that the degrading effects of these adverse characteristics of the mobile radio channel and of interference can be mitigated by diversity. The way how diversity influences cellular spectrum efficiency is derived in general. As a reference point, the types of diversity used in GSM are analyzed. In GSM, the potential for diversity enhancement inherent in code-division multiple-access (CDMA) is not exploited. A joint detection code-division multiple-access (JD-CDMA) system concept aimed at third generation mobile radio systems has been proposed which introduces a CDMA feature into systems based on time-division multiple-access (TDMA) and frequency-division multiple-access (FDMA) like GSM and also advanced TDMA (ATDMA). The gains achievable by different types of diversity in GSM as well as in the JD-CDMA system concept are investigated. It is shown that considerable gains can be achieved by different types of antenna diversity and by exploiting the additional diversity potential of CDMA. Therefore, third generation standards should be flexible in order to allow the use of as many types of diversity as possible to enhance the cellular spectrum efficiency.

A bandwidth reservation protocol for speech/data integration in TDMA-based advanced mobile systems

Abstract: The traffic performance of third generation mobile systems is greatly influenced by the multiple access protocols used in the radio access subsystem. The paper introduces an access protocol, SIR (service integration radio access), which has the potential for accommodating the requirements of speech and bursty data traffic in an efficient way. SIR is evolved from a protocol (PRMA++) studied in the framework of a TDMA-based version of the European Universal Mobile Telecommunication System, UMTS, and uses dedicated mechanisms for data bandwidth request collection and servicing.

Method to increase capacity in DECT

Abstract: The invention relates to a method at a digital radio communication system such as DECT which makes possible to increase said system with further frequency bands with retaining of the dynamic channel allocation and with possibility to at the same time, within the same time frame, be able to use both the frequency bands. This is attended to by that a time slot in DECT's time slot structure is given a special function which results in that, when a base unit at channel scanning reaches said time slot, a scanning etc starts within the ISM-band and if the dynamic channel allocation algorithm (DCA) chooses to use the time slot, then base station and portable will switch themselves for transmission on the ISM-band. Further there is a time slot on the ISM-band which in corresponding way functions as communication link towards the 1800 MHz-band, at which if the dynamic channel allocation algorithm chooses to utilize this time slot, base station and portable switch themselves for transmission on the 1800 MHz-band.

Time-reuse partitioning system and methods for cellular radio telephone systems

Abstract: Time slots of a plurality of time-division multiple access (TDMA) cellular radiotelephone base stations are synchronized. Cellular radiotelephone frequencies are allocated among the plurality of base stations according to a first frequency allocation system in a first synchronized time slot and according to a second frequency allocation system in a second synchronized time slot. Each frequency allocation system may include an adaptive channel allocation system, a frequency reuse system, a frequency reuse partitioning system or a fixed frequency reuse system. Spreading codes of a plurality of code-division multiple access (CDMA) cellular radiotelephone base stations are synchronized. Cellular radiotelephone frequencies are allocated among the plurality of base stations according to a first frequency allocation system for a first synchronized spreading code and according to a second frequency allocation system for a second synchronized spreading code. Each frequency allocation system may include an adaptive channel allocation system, a frequency reuse system, a frequency reuse partitioning system or a fixed frequency reuse system. Cellular radiotelephone systems and methods affording increased base station channel capacity, more efficient spectrum utilization and improved equipment migration are thus provided.