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Showing papers on "Channel allocation schemes published in 1994"


Journal ArticleDOI
01 Sep 1994
TL;DR: In this article, a hierarchical overlaid scheme suitable for high-capacity microcellular communications systems is considered as a strategy to achieve high system performance and broad coverage, where high-teletraffic areas are covered by microcells while overlaying macrocells cover low-TEFL areas and provide overflow groups of channels for clusters of microcells.
Abstract: A hierarchical overlaid scheme suitable for high-capacity microcellular communications systems is considered as a strategy to achieve high system performance and broad coverage. High-teletraffic areas are covered by microcells while overlaying macrocells cover low-teletraffic areas and provide overflow groups of channels for clusters of microcells. New calls and handoff calls enter at both the microcell and macrocell levels. Handoff calls are given priority access to channels at each level. The layout has inherent load-balancing capability, so spatial teletraffic variations are accommodated without the need for elaborate coordination of base stations (wireless gateways). An analytical model for teletraffic performance (including handoff) is developed. Theoretical performance characteristics that show carried traffic as well as blocking, handoff failure, and forced termination probabilities are derived. Effects of nonuniform teletraffic demand and channel allocation strategies on system performance are discussed. >

190 citations


Journal ArticleDOI
TL;DR: This work determines the call blocking performance of channel-allocation algorithms where every channel is available for use in every cell and where decisions are made by mobiles/portables based only on local observations and suggests that an aggressive algorithm could provide a substantially reduced blocking probability.
Abstract: We determine the call blocking performance of channel-allocation algorithms where every channel is available for use in every cell and where decisions are made by mobiles/portables based only on local observations. Using a novel Erlang-B approximation method, together with simulation, we demonstrate that even the simplest algorithm, the timid, compares favorably with impractical, centrally administered fixed channel allocation. Our results suggest that an aggressive algorithm, that is, one requiring call reconfigurations, could provide a substantially reduced blocking probability. We also present some algorithms which take major steps toward achieving the excellent blocking performance of the hypothetical aggressive algorithm but having the stability of the timid algorithm. >

118 citations


Patent
19 Dec 1994
TL;DR: In this article, the authors present a channel hopping scheme for a cellular TDMA mobile radio communication system with channel hopping, which is free from coincidence on any radio channel with any other of the schemes used for transmission within the same cell.
Abstract: According to method and apparatus for communication in a cellular TDMA mobile radio communication system with channel hopping, base and mobile stations transmit radio signal bursts in time slots of a plurality of radio channels in accordance with channel hopping schemes. All of the schemes used by a base and mobile stations in a cell are free from coincidence on any radio channel with any other of the schemes used for transmission within the same cell. A scheme used by a mobile station in one cell occasionally coincides on a radio channel with a scheme used by a mobile station in another cell. The major part of every channel shifting scheme used by a mobile station in a cell is free from coincidence on any radio channel with the major part of any channel hopping scheme used by a mobile station in another cell. The signal to interference ratio or other signal characteristics such as signal strength or bit error rate for signals received by mobile stations are estimated and compared, and the output power of stations are controlled. The existence of further possible channel hopping schemes in a cell, free from coincidence on every radio channel with every other of the channel hopping schemes already in use in that cell, is checked. When another connection to a particular mobile is desired and there is a possible mobile scheme free from coincidence, the desired connection is established using the possible channel hopping scheme in the cell, only if the estimated C/I for certain mobile stations involved in connections exceeds a minimum level.

100 citations


Patent
Harri Jokinen1, Esa Malkamaeki1
25 May 1994
TL;DR: In this paper, the authors proposed a communication method for a digital cellular mobile telephone system and a DMA system consisting of several base stations and mobiles utilizing time division multiple access.
Abstract: The invention relates to a communication method for a digital cellular mobile telephone system and a digital cellular mobile telephone system comprising several base stations and mobiles utilizing time division multiple access. In the system communication is carried out on a predetermined frequency band in a predetermined number of time slots having a predetermined length. In the communication between the mobiles and the base station within the TDMA time slot with the predetermined length, the transmissions to communicate information comprising a few bits or several bits from the mobiles communicating with the same base station at least within the same time slot are mutually substantially orthogonal. Preferably, in order to communicate information, preferably information of the on-off type, such as acknowledgments and channel allocation requests, the mobiles communicating with the same base station use substantially orthogonal transmissions at least to the same base station in the same time slot. Preferably each mobile transmits within the TDMA burst of said TDMA time slot of the predetermined length as a part of the burst a predetermined bit sequence corresponding to the transmitted information bit combination, whereby the predetermined frequency band is unchanged. The bit sequences transmitted by different mobiles to the same base station are mutually substantially orthogonal. By using such substantially orthogonal transmissions it is possible to avoid collisions between the communications of information comprising a few or several bits, typically 1 to 10 bits, such as acknowledgments and channel allocation requests, which typically occur in a time division multiple access system.

97 citations


Proceedings ArticleDOI
08 Jun 1994
TL;DR: A simple speed estimation is proposed and based on this estimate one can implement a number of dynamic channel allocation algorithms on such a hierarchical network which comprises cells of different sizes.
Abstract: The huge amount of handoffs generated by microcells creates a problem for the future PCN. To alleviate the problem, we propose a hierarchical cellular system which comprises cells of different sizes. Ideally, one would like to use large cells to serve high-mobility users. A challenging issue is to obtain a good estimate of the user speed. A simple speed estimation is proposed and based on this estimate one can implement a number of dynamic channel allocation algorithms on such a hierarchical network. A comparative study of these algorithms will be presented based on a detailed simulation model. >

88 citations


Book ChapterDOI
01 Jan 1994
TL;DR: In this article, the concept of achievable C/I, up/down-link equivalence and C/balancing is introduced, and the results show that substantial improvements in system capacity can be achieved, particulary in conjunction with dynamic channel allocation.
Abstract: Transmitter power control is a necessity to combat “near-far” problems in radio systems using receivers with limited “dynamic range” (such as conventional DSCDMA systems). Transmitter power control, however, can also be used to control cochannel interference, i.e. interference from other users using the same channel (code or time slot). For this purpose, it has been shown that the optimum transmitter power configuration is found by solving an eigenvalue problem. The paper reviews some recent results in this area. The basic models as well as the concepts of achievable C/I, up/down-link equivalence and C/Ibalancing are introduced. Both the interference limited (noise-less) case as well as models including thermal noise are treated. Results show that substantial improvements in system capacity can be achieved, particulary in conjunction with Dynamic Channel Allocation. The optimum power control schemes are shown to be robust against implementational shortcomings.

82 citations


Patent
15 Dec 1994
TL;DR: In this article, the authors present a system and methods for allocating channels in a radiotelephone system wherein local estimation of interference for a potential new connection is achieved by measuring interference on the available downlink channels at a plurality of locations within a cell.
Abstract: The present invention relates to systems and methods for allocating channels in a radiotelephone system wherein local estimation of interference for a potential new connection is achieved by measuring interference on the available downlink channels at a plurality of locations within a cell The measurements can be made, for example, by already connected mobile stations, mobile stations which are not connected, fixed measurement stations or any combination thereof

75 citations


Journal ArticleDOI
TL;DR: It is concluded that the proposed multistage neural network approach is well-suited to the dynamic channel allocation problem of future cellular or microcellular systems with decentralized control.
Abstract: Conventional dynamic channel assignment schemes are both time-consuming and algorithmically complex An alternative approach, based on cascaded multilayered feedforward neural networks, is proposed and examined on two cellular systems with different configurations Simulation results showed that the blocking performance of our multistage neural network approach can match that of an example conventional scheme with less complexity and higher computational efficiency The example scheme considered here is the ordered channel search, which can achieve a reasonably high spectral efficiency as compared to that of an ideal dynamic channel allocation algorithm We conclude that our neural network approach is well-suited to the dynamic channel allocation problem of future cellular or microcellular systems with decentralized control >

72 citations


Patent
18 Jul 1994
TL;DR: In this article, a two-way multi-media communication system with a central controller, a shared transmission media, and a plurality of remote terminals dispersed throughout the network is presented, where the communication channels between the central controller and remote terminals are arranged for signalling data and traffic in the forward and reverse directions.
Abstract: There is provided a dynamic and adaptable method and apparatus to support two-way multi-media communication services on a multiple access communication system, which comprises a central controller, a shared transmission media and a plurality of remote terminals dispersed throughout the network. The central controller comprises switch and control apparatus and a pool of transmitters and receivers. The communication channels between the central controller and remote terminals are arranged for signalling data and traffic bearer channels in the forward and reverse directions. The number of signalling data channels is adjusted to satisfy the traffic requirements and for redundancy purposes. The forward and reverse signalling data channels are coupled in different mappings to support terminal grouping. Multiple access of the remote terminals for the upstream traffic are mitigated by separating remote terminals in groups via the channel allocation and the terminal assignment process. Communication between the central controller and the remote terminals follows a multiple access scheme controlled by the central controller via polling procedure on each of the forward signalling data channels independently. In case of collision, the central controller engages the remote terminals in a selective polling process to resolve the contention. The overlapping polling method of the controlled access scheme increases the utilization of the signalling channel and reduces the time required to gain access to the shared transmission media. By dynamically adjusting the load on signalling data channels, the signalling process is greatly improved for efficiency and redundancy against anomalies with the added benefit of improved flexibility and extensibility. The system is especially useful in a two-way CATV network.

65 citations


Journal ArticleDOI
TL;DR: In this paper, the authors model a cellular network as a more general multiple service, multiple resource system and define the state of the system as the number of calls currently carried in each cell.
Abstract: We model a cellular network as a more general multiple service, multiple resource system. We define the "state" of the system as the number of calls currently carried in each cell. We restrict ourselves to channel allocation policies that place restrictions on the global state of the system, are allowed immediate global channel reallocation, and ignore handoffs. Maximum packing and fixed allocation are considered as special cases of such policies. Under uniform load conditions, we prove that throughput is increasing and concave with respect to increases in load or capacity, under maximum packing or fixed allocation. We propose that the optimal policy, in the considered class, varies from maximum packing at low loads to fixed allocation at high loads. This policy is often impractical to implement, but can be considered as a performance bound on practical systems. The analytical results are investigated numerically using a simple seven cell linear network. >

50 citations


Patent
Kojiro Hamabe1
27 Dec 1994
TL;DR: In this paper, a base station determines the arrival directions of interference waves on all channels and the arrival direction of the desired waves from the wireless terminal, selects channel in order for which the difference between arrival directions between interference waves and desired waves are closest to 180° and allocates the first channel to satisfy allocation conditions.
Abstract: In this invention, base stations established in service areas use sector antennas to cover a multiplicity of sector cells. When a communication request arises between a wireless terminal and a sector cell within the sector cell, the base station determines the arrival directions of interference waves on all channels and the arrival direction of the desired waves from the wireless terminal, selects channel in order for which the difference between arrival directions of interference waves and desired waves are closest to 180° and allocates the first channel to satisfy allocation conditions.

Patent
Kanai Toshihito1
17 May 1994
TL;DR: In this paper, the authors proposed a channel allocation method which achieves a high frequency utilization efficiency while suppressing the average transmission power by transmission power control, where selection priority degrees and initial minimum transmission power controlling amounts are set for all radio channels allocated to the system.
Abstract: The invention provides channel allocation method which achieves a high frequency utilization efficiency while suppressing the average transmission power by transmission power control. Selection priority degrees and initial minimum transmission power control amounts are set for all radio channels allocated to the system. The initial minimum transmission power control amounts are set such that the radio channel having higher selection priority degree has higher or at least equal initial minimum transmission power control amount than the lower selection priority radio channel. Upon channel allocation, a radio channel is selected in accordance with the selection priority degree, by the way that calculating the transmission power control amount of the radio channel (S505 to S507), comparing the transmission power control amount with the initial minimum transmission power control amount (S508), and when the transmission power control amount is equal to or higher than the initial minimum transmission power control amount, then use of the radio channel is permitted.

Proceedings ArticleDOI
28 Nov 1994
TL;DR: A class of non-reserving policies that efficiently utilize the channels is defined and a most critical first policy is identified that is optimal with respect to handover failure probability and has the best channel utilization in its class.
Abstract: In cellular systems, a primary goal is the reduction of handover failures in the system. Channel allocation policies that address this by setting aside guard channels for the exclusive use of handover requests suffer from a lower utilization of the scarce channel resources. We define a class of non-reserving policies that efficiently utilize the channels. Within this class, we identify a most critical first policy that is optimal with respect to handover failure probability. Moreover, this policy is shown to have the best channel utilization in its class as well. The proofs of optimality are accompanied by the description of a technique to realize the policy in practice. Simulation results that demonstrate its improvement over previous policies are presented as well.

Journal ArticleDOI
TL;DR: This work combines autonomous algorithms for dynamic channel assignment (DCA) and power control in a TDMA/FDMA wireless system as a medium access control (MAC) protocol that can be applied in different wireless communications environments.
Abstract: We combine autonomous algorithms for dynamic channel assignment (DCA) and power control in a TDMA/FDMA wireless system as a medium access control (MAC) protocol. The DCA algorithm determines paired radio channels that experience the least interference and are least likely to cause interference. The power control algorithm uses local estimations of signal to interference ratio (SIR) at a receiver to iteratively command power adjustment on the desired transmitter. A common control frequency, which is frame-synchronized among base stations, provides all necessary information for DCA without blind slots. Computer simulations are used to evaluate system performance. Results from computer simulations demonstrate good spectrum efficiency and robustness. Although studied under a specific set of parameters, this type of MAC protocol can be applied in different wireless communications environments. >

Proceedings ArticleDOI
08 Jun 1994
TL;DR: This work combines autonomous algorithms for dynamic channel assignment (DCA) and power control in a TDMA/FDMA wireless system as a medium access control (MAC) protocol that can be applied in different wireless communications environments.
Abstract: We combine autonomous algorithms for dynamic channel assignment (DCA) and power control in a TDMA/FDMA wireless system as a medium access control (MAC) protocol. The DCA algorithm determines paired radio channels that experience the least interference and are least likely to cause interference. The power control algorithm uses local estimations of signal to interference ratio (SIR) at a receiver to iteratively command power adjustment on the desired transmitter. A common control frequency, which is frame-synchronized among base stations, provides all necessary information for DCA without blind slots. Computer simulations are used to evaluate system performance. Results from computer simulations demonstrate good spectrum efficiency and robustness. Although studied under a specific set of parameters, this type of MAC protocols can be applied in different wireless communications environments. >

Patent
19 Aug 1994
TL;DR: In this paper, a system of the subject invention includes a mobile telecommunications switching office (MTSO), several base stations and mobile units, where the base stations are connected to the MTSO which performs switching to establish call connections between mobile units and/or between units served by an external network.
Abstract: A system of the subject invention includes a mobile telecommunications switching office (MTSO), several base stations and mobile units. The base stations serve respective sectors or cells to establish radio communications with mobile units in their sectors or cells. The base stations are connected to the MTSO which performs switching to establish call connections between mobile units and/or between units served by an external network to which the MTSO is connected. The MTSO uses dynamic channel allocation to designate base stations to serve a call connection in active mode and in standby mode for a particular channel. Therefore, if communication with the base station serving a call connection in active mode is disrupted by a building, terrain or an equipment failure, for example, the MTSO can set the base station currently in active mode to standby mode, and can set the base station currently in standby mode, to active mode to serve the call connection on the channel. Thus, the use of sectors or cells in active and standby modes, allows for relatively reliable communications through macro-diversity. Also, the ping-pong effect occurs relatively infrequently because the sectors or cells are switched between active and standby modes as a mobile unit moves along a sector or cell boundary, rather than requiring a handoff to another channel as required in conventional systems. Further, through use of dynamic channel allocation, handoffs in the traditional sense are relatively rare in the system of the subject invention.

Proceedings ArticleDOI
08 Jun 1994
TL;DR: It is shown that under non-uniform traffic loading a better grade-of-service can be provided to network subscribers than by fixed channel assignment, and the network performance measures used in this paper are the average and maximum probability of blocking across the network.
Abstract: We examine several methods to allocate radio frequency channels across a cellular network. In this paper we consider centralized channel assignment strategies that utilize global network traffic information. The channel assignment methods considered are linear programming, quadratic programming, and a heuristic algorithm to assign resources given the network traffic loading. Each method attempts to assign resources, under frequency reuse constraints, to achieve a desired target performance measure for the network. The network performance measures used in this paper are the average and maximum probability of blocking across the network. We compare the performance of a linear highway network and a planar network using our assignment methods to those of uniform fixed channel allocation (FCA) for non-uniform network traffic loading. We show that under non-uniform traffic loading a better grade-of-service can be provided to network subscribers than by fixed channel assignment. >

Journal ArticleDOI
TL;DR: The performance of the novel DCA technique in terms of call blocking probability has been derived by simulations and results are compared with those achieved by a fixed channel allocation (FCA) technique to show a better behaviour.
Abstract: This paper deals with an efficient dynamic channel allocation (DCA) technique suitable for applications in mobile satellite cellular networks. A cost function is defined to allow an optimum selection of channels to be allocated on demand. A mobility model suitable for low earth orbit (LEO) satellite systems is presented. The performance of the novel DCA technique in terms of call blocking probability has been derived by simulations. The obtained results are compared with those achieved by a fixed channel allocation (FCA) technique to show a better behaviour.

Proceedings ArticleDOI
12 Jun 1994
TL;DR: The authors develop an efficient algorithm to compute the minimum capacity required to satisfy all the QOS requirements when multiple classes of on-off sources are multiplexed onto a single VP.
Abstract: For future broadband-ISDN, asynchronous transfer mode (ATM) is designed not only to support a wide range of traffic classes with diverse flow characteristics (e.g., burstiness, bit rate and burst length), but to guarantee the different quality of service (QOS) requirements as well. The QOS may be measured in terms of cell loss probability and maximum cell delay. The authors consider the ATM network in which the virtual path (VP) concept is implemented. By applying the Markov modulated deterministic process method, they develop an efficient algorithm to compute the minimum capacity required to satisfy all the QOS requirements when multiple classes of on-off sources are multiplexed onto a single VP. Using the result, they then propose a simple algorithm to determine the VP combination to achieve the near optimum of the total capacity required for satisfying the individual QOS requirements. Numerical results are also presented to demonstrate the performance of the algorithm when compared to the optimal total capacity required. >

Journal ArticleDOI
TL;DR: Computer simulation demonstrates that the bit error rate (BER) performance and the spectral efficiency of the trellis-coded 16QAM/TDMA cellular system are superior to those of /spl pi//4-QPSK/ TDMA used in the American and Japanese digital cellular standards.
Abstract: Trellis-coded 16QAM/TDMA systems are proposed that have a high spectral efficiency and high transmission quality and that can support a wide variety of services. A digital pilot-symbol-aided channel sounding scheme, as well as diversity reception with maximal ratio combining, are used to compensate for fading. To further improve transmission quality, symbol interleaving and two-frequency hopping are used in the trellis-coded 16QAM/TDMA system. Computer simulation demonstrates that the bit error rate (BER) performance and the spectral efficiency of the trellis-coded 16QAM/TDMA cellular system are superior to those of /spl pi//4-QPSK/TDMA used in the American and Japanese digital cellular standards. It is also demonstrated that the trellis-coded 16QAM/TDMA with diversity, symbol interleaving, and frequency hopping can achieve a BER of about 10/sup -4/ if the delay spread is 0.1 T/sub s/. >

Proceedings ArticleDOI
Chih-Lin I1, Pi-Hui Chao
18 Sep 1994
TL;DR: The results show that although the ACI constraint may significantly reduce the traffic adaptation capability of DCA in general, the LP-DDCA is quite robust with respect to this additional constraint.
Abstract: Dynamic channel allocation (DCA) has become an important subject of research and development for wireless/cellular networks. Various DCA schemes have been proposed and numerous studies on their performance have been made. However, the DCA investigations so far have all been done under the constraints imposed by co-channel interference only. Another important constraint which is crucial in practical systems, namely, the channel usage limited by adjacent channel interference (ACI), has mostly been overlooked in the literature. The authors analyze the ACI constraints under various spatial relationships between the mobile and base stations. They also make the first attempt to investigate the impact of this constraint on DCA by devising a modified version of a novel and practical distributed DCA algorithm, the local packing DDCA (LP-DDCA), incoporating the ACI constraint. Then, the performance improvement offered by the modified LP-DDCA is re-evaluated. The results show that although the ACI constraint may significantly reduce the traffic adaptation capability of DCA in general, the LP-DDCA is quite robust with respect to this additional constraint.

Proceedings ArticleDOI
01 May 1994
TL;DR: A parameter is proposed as a quality factor for measuring, in real-time, the reliability of the communication link, and helps decision making for on-line network management such as dynamic channel allocation and adaptive power control.
Abstract: A theoretical approach is presented for estimating the quality of signal reception, in an indoor mobile communication system with high transmission bit-rate. A frequency-selective channel model is used for M-ary PSK modulated signals corrupted by additive white noise and interference under Nagakami-Rice fading conditions. Subsequently, the problem of finding a practical way to determine the level of interference (due to frequency reuse from neighbouring microcells and due to the multipath delay spread) is addressed. Thus, a parameter is proposed as a quality factor for measuring, in real-time, the reliability of the communication link. The proposed method helps decision making for on-line network management such as dynamic channel allocation and adaptive power control. >

Patent
Andrew John Booth1
15 Jul 1994
TL;DR: In this paper, the authors proposed a handover method for a call associated with a mobile station in one cell but moving towards another cell, where the mobile station is allocated a different channel in the one cell and makes a second attempt.
Abstract: A method of performing handover of a call associated with a mobile station in one cell but moving towards another cell includes making a first attempt, using for example a MUX1 SNIFF procedure, on the channel allocated to the mobile station for that call. If that attempt fails, the mobile station is allocated a different channel in the one cell and makes a second attempt. This different channel allocation (intracell handover) is performed even if there are no better signal characteristics achieved as a result. This procedure makes it more likely to be possible to achieve handover when a second mobile station associated with an adjacent cell and operating on the same channel as the first mobile station is also within range of the base station of the other cell.

Journal ArticleDOI
TL;DR: This work investigates the elementary case where there is only a single channel available for use in the system, and determines the capacity for infinite linear and planar arrays of microcells using a very idealized environment.
Abstract: One important quantity in assessing the viability of local, autonomous, dynamic channel allocation for microcellular systems is user capacity, defined as the average number of users per channel per cell. Here, we determine the capacity for infinite linear and planar arrays of microcells using a very idealized environment. In particular, propagation and interference considerations are simply represented by the constraint that, if a channel is used in a given cell, it cannot be used in R-consecutive rings of cells around that cell. We investigate the elementary case where there is only a single channel available for use in the system. Using this representation, we compute the best and worst user capacities as well as the capacity achieved by random channel placement. While the environment under which these capacities are derived is highly idealized, the results are useful in two important ways. First, the best capacity and the random channel placement capacity we find here for single-channel, self-organized access are fundamental for computing the traffic characteristics of important multichannel dynamic channel allocation algorithms. Second, the random channel placement capacity is close enough to the best that can be achieved to suggest that local, autonomously implemented, dynamic channel allocation loses little capacity when compared with centrally administered fixed channel allocation. >

Journal ArticleDOI
TL;DR: This paper considers large cellular mobile networks with dynamic channel allocation in which the arrival rates, holding times and handover probabilities for the different cells are identical.
Abstract: This paper considers large cellular mobile networks with dynamic channel allocation in which the arrival rates, holding times and handover probabilities for the different cells are identical. Such networks could model, for example, cellular networks in suburban areas. Different methods of analysing these networks are compared. These methods fall into two basic categories, those which approximate a network with a smaller finite network and those which consider the expected performance of a cell within an environment consisting of cells with identical properties. Simplifications of these methods which arise out of the reversibility of a symmetric cellular network are also discussed.

Journal ArticleDOI
TL;DR: It is concluded that the spectrum efficiency can be achieved in wireless PCS systems by applying the intelligent cell concept by solving the dilemma of how to reduce interference in the face of interference.
Abstract: We have concluded that the spectrum efficiency can be achieved in wireless PCS systems by applying the intelligent cell concept. The intelligent cell can either reduce interference by intelligently delivering the signal to the mobile unit, or can tolerate a great deal of interference while receiving with it. The former isolates the signal with multiple zones. In the latter, the signal resides with the interference but retains its processing gain. This paper presents the philosophy of achieving spectrum efficiency by applying the intelligent cell concept in wireless PCS systems. >

Journal ArticleDOI
TL;DR: In this article, the feasibility of optimizing the frequency spacing between carriers such that the combined effect of distance and IF filter will be enough to control the interference while allowing the maximum number of channels in a given bandwidth was studied.
Abstract: In FDMA cellular radio systems, the adjacent channel interference (ACI) is suppressed by the IF filter and also by a distance factor. Channels immediately adjacent to each other in frequency are assigned to different cells and, as such, the distance plays a role in reducing their mutual interference. The authors study the feasibility of optimizing the frequency spacing between carriers such that the combined effect of distance and IF filter will be enough to control the interference while allowing the maximum number of channels in a given bandwidth. They also study the decision feedback equalizer (DFE) as a means to reduce any excess ACI that results from reducing the channel spacing. The paper starts with a model that estimates the cumulative probability density of the signal to adjacent channel interference ratio (SIR) as a function of the channel spacing. They then present the results of a computer simulation study to estimate the performance of DFE in mitigating the effect of ACI. The results indicate that, under the conditions of slow flat fading and selection diversity, the DFE is very effective in reducing the effect of excess ACI interference which allows for a considerable reduction in the frequency spacing. >

Patent
Kanai Toshihito1
18 May 1994
TL;DR: In this paper, the authors proposed a channel allocation method which achieves a high frequency utilization efficiency while suppressing the average transmission power by transmission power control, where selection priority degrees and initial minimum transmission power controlling amounts are set for all radio channels allocated to the system.
Abstract: The invention provides channel allocation method which achieves a high frequency utilization efficiency while suppressing the average transmission power by transmission power control. Selection priority degrees and initial minimum transmission power control amounts are set for all radio channels allocated to the system. The initial minimum transmission power control amounts are set such that the radio channel having higher selection priority degree has higher or at least equal initial minimum transmission power control amount than the lower selection priority radio channel. Upon channel allocation, a radio channel is selected in accordance with the selection priority degree, by the way that calculating the transmission power control amount of the radio channel (S505 to S507), comparing the transmission power control amount with the initial minimum transmission power control amount (S508), and when the transmission power control amount is equal to or higher than the initial minimum transmission power control amount, then use of the radio channel is permitted.

Proceedings ArticleDOI
27 Jun 1994
TL;DR: Centralized and distributed dynamic channel allocation (DCA) algorithms which allow users to have different SIR requirements have been developed to maximize the capacity of the system under a desired blocking probability.
Abstract: In a conventional TDMA wireless system, the blocking probability is affected by the worst case interference statistics. Modifying the system to a frequency-hopped CDMA (CDMA-FH) system can change the blocking probability to be determined by average statistics. Hopping patterns can be implemented easily using Latin squares. A system using Latin squares of size n guarantees no users in the same cell share any slots and a user and all users in different cells share only one out of every n slots. Channel coding over hops then suppresses the worst interference. Further improvements may be obtained by allowing users to occupy M out of N slots where M/spl les/N. Centralized and distributed dynamic channel allocation (DCA) algorithms which allow users to have different SIR requirements have been developed to maximize the capacity of the system under a desired blocking probability. >

Journal ArticleDOI
TL;DR: A control architecture for implementing a dynamic channel assignment (DCA) algorithm which optimizes two-way channel quality in a TDMA portable radio system is proposed and good spectrum efficiency and its potential for handling nonuniform traffic demand are demonstrated.
Abstract: We propose a control architecture for implementing a dynamic channel assignment (DCA) algorithm which optimizes two-way channel quality in a TDMA portable radio system. Computer simulations are used to evaluate the performance of this DCA method. A common control frequency, which is frame-synchronized among base stations, provides (1) beacons for portables to locate base stations and obtain DCA information, (2) broadcast channels for system and alerting information, and (3) pilot signals to permit portables to evaluate downlink interference. This allows low-complexity radio ports and portables to mutually select channels to avoid interference and avoid creating excessive interference. Results from computer simulations demonstrate the good spectrum efficiency of this method and its potential for handling nonuniform traffic demand. This work is targeted toward understanding the implications to local exchange networks of wireless system alternatives that could provide access to those networks.