Showing papers on "Channel allocation schemes published in 1995"

Effective bandwidth in high-speed digital networks

Abstract: The theory of large deviations provides a simple unified basis for statistical mechanics, information theory and queueing theory. The objective of this paper is to use large deviation theory and the Laplace method of integration to provide an simple intuitive overview of the theory of effective bandwidth for high-speed digital networks, especially ATM networks. This includes (1) identification of the appropriate energy function, entropy function and effective bandwidth function of a source, (2) the calculus of the effective bandwidth functions, (3) bandwidth allocation and buffer management, (4) traffic descriptors, and (5) envelope processes and conjugate processes for fast simulation and bounds. >

Method and system for channel allocation using power control and mobile-assisted handover measurements

Abstract: A method and system for the adaptive allocation of channels within a radio communication system, specifically a cellular network, is presented. The allocation method takes advantage of measurements made by the mobile radiotelephone and allocates channels based on the carrier to interference ratio. Using adaptive power control, consideration is given to maintaining an acceptable carrier to interference ratio while at the same time minimizing transmit power. Exemplary embodiments consider independent allocation of the uplink and downlink as well as independent determination of the uplink and downlink power levels. Other exemplary embodiments also give consideration to an efficient method for slot allocation in a TDMA communication system.

Handover and dynamic channel allocation techniques in mobile cellular networks

Abstract: This paper deals with an efficient dynamic channel allocation (DCA) technique applicable to terrestrial mobile cellular networks. A channel (or resource) is a fixed frequency bandwidth (FDMA), a specific time-slot within a frame (TDMA), or a particular code (CDMA), depending on the multiple access technique used. A cost function has been defined by which the optimum channel to be assigned on demand can be selected. In addition, a suitable mobility model has been derived to determine the effects of handovers on network performance. The performance of the proposed DCA technique has been derived by computer simulations in terms of call blocking and handover failure probabilities. Comparisons with the classical fixed channel allocation (FCA) technique and other dynamic allocation algorithms recently proposed in the literature have been carried out to validate the proposed technique. >

Efficient dynamic channel allocation techniques with handover queuing for mobile satellite networks

Abstract: Efficient dynamic channel allocation techniques with handover queuing suitable for applications in mobile satellite cellular networks, are discussed. The channel assignment on demand is performed on the basis of the evaluation of a suitable cost function. Geostationary and low Earth orbit (LEO) satellites have been considered. In order to highlight the better performance of the dynamic techniques proposed, a performance comparison with a classical fixed channel allocation (FCA) has been carried out, as regards the probability that a newly arriving call is not completely served. It has also been shown that a higher traffic density, with respect to GEO systems, is manageable by means of LEO satellites. >

Mobile communication system with autonomous distributed type dynamic channel allocation scheme

Abstract: A mobile communication system using an autonomous distributed type dynamic channel allocation scheme, in which each base station manages allocation priority levels for the available radio channels according to past records of channel use for each radio channel, and updates the allocation priority level of each radio channel by weighting past allocation accept/reject judgement results for each radio channel with weight factors which vary according to time intervals of the past allocation accept/reject judgement results from a current time. The mobile stations can be grouped into N groups according to states of the mobile stations and N sets of allocation priority levels for each radio channel in correspondence to these N groups can be managed at each base station. The thresholds for grouping the mobile stations can be determined according to past records of states of the mobile stations.

Channel hopping in a radio communications system

Abstract: The invention relates to a method and to an arrangement for effecting base orthogonal channel hopping between mobile stations (MS1-MS3) and a base station in a radio communications system. Connections (F1-F3) having low attenuation are allotted a number of channels having high interference I (channel, t). Connections (F1-F3) that have higher attenuation are allocated a number of channels that have lower interference I (channel, t). A channel allocation means (211) in the base station functions to produce channel hopsequences which are transferred to hopsequence lists (204-206) in the mobile stations (MS1-MS3), via a control channel SACCH. The channel hopsequences are also transferred to corresponding hopsequence lists (201-203) in the base station. Attenuation of the connections (F1-F3) and interference on the channels I (channel, t) are measured continuously in the channel allocating means (211), wherein the best channels with respect to interference are used. The channel allocation means creates the channel hop sequences in accordance with the principle that the better a connection with respect to attenuation, the poorer the channels with respect to interference that are allocated to the connection.

Distributed autonomous wireless channel assignment algorithm with power control

Abstract: Local autonomous dynamic channel allocation (LADCA) including power control is essential to accommodating the anticipated explosion of demand for wireless. The authors simulate call performance for users accessing channels in a regular cellular array with a base located at the center of each hexagon. The computer model includes stochastic channel demand and a propagation environment characterized by attenuation with distance as well as shadow fading. The study of LADCA shows that distributed power control and channel access can be combined in an access management policy that achieves satisfactory system capacity and provides desired call performance. The authors report: LADCA/power control is observed to be stable alleviating a major concern about users unaware of the signal to interference problems their presence on a channel might cause to others. There can be substantial inadvertent dropping of calls in progress caused by originating calls. Modeling user time dynamics is essential. LADCA contrasts very favorably with fixed channel allocation (FCA) in a comparative example. >

Distributed dynamic channel allocation for mobile computing

Abstract: Efficient allocation of communication channels is critical for the performance of wireless mobile computing systems. The centralized channel allocation algorithms proposed in literature are neither robust, nor scalable. Distributed channel allocation schemes proposed in the past are complicated and require active participation of the mobile nodes. These algorithms are unable to dynamically adjust to spatial and temporal fluctuations in channel demand. We present a dynamic distributed channel allocation algorithm that can quickly adapt to changes in load distribution. The algorithm described in this paper requires minimal involvement of the mobile nodes, thus conserving their limited energy supply. The algorithm is proved to be deadlock free, starvation free and fair. It prevents co-channel interference and is scalable.

The geometric dynamic channel allocation as a practical strategy in mobile networks with bursty user mobility

Abstract: In this paper we refer to a specific class of Dynamic Channel Allocation (DCA) strategies, namely the interferencefree, timid, not-conditioned class. The main concern of this work is to verify if and to what extent strategies belonging to this class can offer better performance than Fixed Channel Allocation (FCA). The interest in this kind of strategies is motivated by their feasibility with current TDM technologies, the limited amount of information required to carry out channel assignments and their intrinsic stability. In this framework we present a simple, but very attractive DCA strategy, the so-called Geometric DCA (GDCA). A performance evaluation is carried out to compare some representative DCA strategies of the considered class, by using a user mobility model that accounts for the large fluctuations of the number of users in a cell coverage area expected in a microcellular environment. The effect of the non-null propagation time required by the information exchange in the DCA strategies is also taken into account. It emerges that the proposed GDCA allows better performance than more sophisticated strategies already proposed, at the expense of a frequency planning carried out only at network configuration. This is due to the ability of GDCA to exploit the a priori information to maintain a tight geometric packing of used carriers. The reported results also show that DCA strategies in the considered class cope with large and sudden traffic fluctuations remarkably better than the FCA scheme does and that the advantage becomes more evident as the burstiness of the user mobility process (hence of the offered traffic) increases.

Channel allocation system for distributed digital switching network

Abstract: A channel allocation system for selecting the earliest available switch port and time division multiplexed channel for an outgoing transmission in a network of switch elements interconnected by a series of communications paths. An availability table for maintaining the free/busy state of each channel on each switch port in the switch element is provided. Means are additionally provided for limiting the search of the availability table for the earliest available channel to certain desired switch ports and channels.

Method and apparatus for updating carrier channel allocations

Abstract: In a communication system that utilizes DMT technology to couple a primary site (102) to a plurality of secondary sites (104-108), carrier channel allocations may be updated as follows. At periodic intervals, the primary site requests updating bit loading information from the secondary sites. Upon receiving the updated bit loading information, the primary site (102) determines an updated call bit loading table for each active call. From this, the primary site (102) determines whether current carrier channel allocation provides sufficient bandwidth. When the current carrier channel allocation does not provide the sufficient bandwidth, the primary site modifies the current carrier channel allocation to meet the bandwidth requirements.

A trunked radio frequency communication system for accommodating both frequency and time division based rf communications

Abstract: In a trunked radio communications system, apparatus and methods are provided for transparently updating existing frequency division multiple access (FDMA) communications facilities to accommodate time division multiple access (TDMA) communications TDMA channels are added to existing FDMA sites on an individual basis to increase spectral efficiency and capacity while still being compatible with existing FDMA equipment and protocols For example, the existing FDMA control channel and protocols are used by dual mode sites and dual mode radios A dual mode radio transceiver selectively participates in trunked radio communications in either an FDMA mode and in a TDMA mode Each dual mode radio includes a memory for storing a mode identifier identifying each channel as an FDMA or a TDMA working channel When a channel assignment is made, the dual mode radio determines from that channel mode identifier stored in memory whether to operate in the FDMA or TDMA mode for that particular communication Moreover, dual mode radios expedite synchronization to a TDMA working channel (time slot) using a timing relationship established between the FDMA control channel and the TDMA working channels In the context of multiple site, trunked radio communications, the present invention provides for interoperability between sites and radios which have TDMA communications capabilities and sites and radios which have only FDMA capabilities

Channel allocation and downlink beamforming in an SDMA mobile radio system

Abstract: On the downlink of an SDMA mobile radio system, co-channel interference has to be kept down by beamforming. In this paper two DOA-based beamforming approaches are presented minimizing array signal power while maintaining given signal-to-noise-and-interference ratios for all users. The linear approach is computationally cheap, so that it is suited for channel allocation as well, quickly evaluating the spatial separability of a specific mobile radio scenario. The nonlinear algorithm yields optimum results but only converges quickly, if provided with a good starting point. Therefore, its basic application is burst-to-burst updating of the beamformer.

Method for channel allocation in a cellular communication system

Abstract: The invention relates to a method for allocating radio channels in a cellular communication system, each cell comprising at least one base station (BTS) communicating with the subscriber terminal equipments (MS) by means of a traffic channel specific for each connection, in which method the base station monitors the quality of the available traffic channels. For improving the service ability of the cellular communication system, in the method of the invention upon selecting the traffic channel for the connection between the base station and the terminal equipment, the quality of the connection required by the terminal equipment and the interference level of each possible traffic channel are taken into account.

Virtual path bandwidth allocation in multi-user networks

Abstract: Considers a multi-user network that is shared by noncooperative users. Each user sets up virtual paths that optimize its own, selfish, performance measure. This measure accounts for both the guaranteed call level quality of service, as well as for the cost incurred for reserving the resource. The interaction between the user strategies is formalized as a game. The authors show that this game has a unique Nash equilibrium, and that it possesses a certain fairness property. They investigate the dynamics of this game, and prove convergence to the Nash equilibrium of both a Gauss-Seidel scheme and a Jacobi scheme. They extend their study to various general network topologies.

Channel probing for distributed access control in wireless communication networks

Abstract: Power control in wireless networks is useful for minimizing channel congestion (hence increasing network capacity). In this work, we show how the distributed power control algorithm with active link protection (DCP-ALP) can be used as a channel probing tool that allows a new link trying to access a channel to quickly and autonomously determine whether it can be admitted to it (i.e. whether there is a feasible power configuration for the transmitters such that the link quality requirements on all links are met), which significantly improves the capacity and access time of the network.

System aspects of cellular radio

Abstract: The greatest single factor in enhancing spectral efficiency of a network is the mass deployment of microcells. By this simple technique we can repeatedly and efficiently reuse the precious spectrum. The number of users a network can support is fundamentally dependent on the common air interface (CAI) over which users communicate. User capacity is dependent on many factors, but the cardinal ones are the amount of spectrum the regulators allocate, the size of the radio coverage area from a base station (BS), and the amount of interference a particular radio link can tolerate. In this article we are primarily concerned with the system aspects associated with the CAI. We focus on the critical importance of BS siting. Starting with existing large cells, we deliberate on the problems that might arise in siting BSs in three dimensional microcells, in order to consider suitable multiple access methods for future cellular environments. >

Method of allocating frequency bands to different cells, and TDMA cellular radio system

Abstract: The invention relates to a TDMA cellular radio system, and a method of allocating available frequency bands to different cells in a TDMA cellular radio system wherein at least some of the receivers within the system employ interference cancellation methods for cancelling the effects of co-channel interference in a desired signal. To enable an efficient utilization of interference cancellation methods and the resulting capacity increase in the system, the frequency bands available for the cellular radio system are, according to the method of the invention, so allocated to different cells that groups (50-55) of adjacent service areas are formed in the system, each group employing the same frequency band within the service areas, whereby at least one co-channel signal interfering with the desired signal is significantly stronger than other co-channel interfering signals.

Modeling Handovers in Cellular Mobile Networks with Dynamic Channel Allocation

Abstract: A model for a cellular mobile network is given which uses the dynamic channel allocation strategy proposed by Everitt and Macfadyen Everitt, D. E., N. W. Macfadyen. 1983. Analysis of multicellular mobile radiotelephone systems with loss. British Telecom. Tech. J.137-45.. In this model, handovers of calls from one cell to another are explicitly included. The equilibrium distribution of this network is shown to have product form under certain reversibility conditions. The conditions are restrictive and are, perhaps, unlikely to hold in practical models. However, their study does provide insight into the behavior of cellular systems with dynamic channel allocation. Using the product-form equilibrium distribution we are able to express the blocking probability for new calls, and the blocking probability for handover calls in terms of appropriate normalizing constants. The model is also extended to allow directed retry for handovers in which blocked handover attempts may try to gain access via another cell. This provides differential service for handovers. Again, some reversibility conditions ensure product form, and the blocking probabilities for both new and handover calls are given in terms of normalizing constants.

Channel scanning scheme for signal strength measurement systems and methods

Abstract: Methods and systems for measuring signal strengths of radio signals in radiocommunication systems are described. In many radiocommunication systems, base stations and/or mobile stations take signal strength measurements on various radio channels, e.g., those in neighboring calls, to provide information to the system for channel allocation and handoff decisions. By sorting lists of channels to be measured into frequency order and taking into account a last tuned channel as well as radio specific tuning characteristics, the overall time spent tuning to each channel in the list can be reduced.

Dynamic allocation of channels in a cellular telephone system

Abstract: A cellular communication system has a plurality of cells and a plurality of channels. The plurality of channels includes a plurality of measurable channels for which interference can be measured in both uplink and downlink directions and a plurality of unmeasured channels for which interference are not made in both uplink and downlink directions. The measurable channels, designated probe channels, may be channels for use in a digital system. The unmeasured channels may be channels for use in an analog system, or broadcast channels. A method and apparatus for allocating the plurality of channels comprises initially organizing the plurality of channels into a plurality of channel groups, wherein each channel group includes at least one probe channel, and wherein at least one of the channel groups further includes at least one unmeasured channel. Then, each one of the cells performs an allocation routine comprising the steps of monitoring at least one of the channel groups by making and collecting uplink and downlink interference measurements only on the probe channel of each monitored channel group over a predetermined time period. Then, the collected uplink and downlink interference measurements are analyzed in accordance with an adaptive channel allocation strategy. Finally, a selected one of the monitored channel groups is allocated to the cell in dependence on the analyzed uplink and downlink interference measurements. In this manner, the unmeasured channels are also subjected to an adaptive channel allocation strategy.

Adaptive channel allocation in a mobile communications system

Abstract: In a cellular communication system, a method and apparatus are provided for allocating a channel for use on a connection between a base station and a mobile station in a cell, without making measurements of downlink interference. Throughout the system, uplink and downlink power levels are regulated so that, within each cell, their sum changes by an amount whose magnitude is substantially equal to the magnitude of change in path gain between the mobile station and the base station in that cell, and which sum is opposite in sign to the amount of change in path gain. This power regulation scheme assures that there will be a strong correlation between system-wide measurements of uplink and downlink interference. Therefore, with the power regulation scheme in place, each cell determines uplink carrier to interference (C/I) ratios for the free channels available for use in the cell and selects an acceptable free channel having a C/I value that is within a predetermined acceptable range. If uplink C/I on the acceptable free channel is greater than the uplink C/I value of a channel currently assigned to a connection, then an intra-cell handover is performed so that the connection will be reassigned to the acceptable free channel. This technique is useful for providing an adaptive channel allocation scheme to systems, such as analog cellular communications systems, in which downlink interference measurements cannot be made.

Synchronous bandwidth allocation in FDDI networks

Abstract: It is well known that an FDDI token ring network provides a guaranteed throughput for synchronous messages and a bounded medium access delay for each node/station. However, this fact alone cannot effectively support many real-time applications that require the timely delivery of each critical message. The reason for this is that the FDDI guarantees a medium access delay bound to nodes, but not to messages themselves. The message-delivery delays may exceed the medium-access delay bound even if a node transmits synchronous messages at a rate not greater than the guaranteed throughput. We solve this problem by developing a synchronous bandwidth allocation (SEA) scheme which calculates the synchronous bandwidth necessary for each application to satisfy its message-delivery delay requirement. The result obtained in this paper is essential for effective use of the FDDI token ring networks in supporting such real-time communication as digital video/audio transmissions, and distributed control/monitoring.

Packet data service over GSM networks with dynamic stealing of voice channels

Abstract: The emerging demand for low-cost data services over GSM networks has driven the ETSI to promote the definition of a General Packet Radio Service (GPRS), in which data traffic is carried according to the packet switched mode. We compare the performance of two possible GPRS implementations, respectively based on the static and dynamic allocation of traffic channels. In the dynamic allocation case, packet data services use traffic channels temporarily unused by circuit switched services, without affecting their performance. Moreover, the combined use of the static and dynamic schemes is evaluated and shown to provide enhanced performance for GPRS.

PC-notebook based mobile networking: algorithms, architectures and implementation

Abstract: The integration of multimedia adaptive wireless networking capabilities in a PC-notebook platform are investigated. To support mobile networking, while providing compatibility with the wired infrastructure, new functions are required for topology creation using multihop protocols. To support mobility in a wireless environment, power control and bandwidth allocation are required in conjunction with adaptive wireless modems and rate-adaptive video codecs. A prototype implementation of a wireless node with these capabilities reveals several performance and complexity limitations with current technology. In particular the DOS operating system, the PC shared bus architecture and traditional partitioning of the network and modem functions lead to severe performance losses that are detrimental in wireless networking. For mobile wireless nodes, these limitations are unacceptable. Several ideas are presented for re-architecting the PC-notebook for wireless networking nodes that can substantially improve bandwidth efficiency while overcoming the complexity and power limitations of current technology.

A polynomial-time optimal synchronous bandwidth allocation scheme for the timed-token MAC protocol

Abstract: Numerous methods have been proposed to integrate real-time and non-real-time services of the timed-token medium access control (MAC) protocol. One of the key issues in tailoring the timed-token MAC protocol for real-time applications is the synchronous bandwidth allocation (SEA) problem whose objective is to meet both the protocol and deadline constraints. Several non-optimal local SEA schemes and an optimal global scheme have been proposed previously. Local SEA schemes use only information available locally to each node, and are thus preferred to global schemes because of their lower network-management overhead. Unfortunately it has been formally proved in Han et al. (1995) that there does not exist any optimal local SEA scheme. Chen et al. [1992] proposed the only-known optimal global SEA scheme which is based on an iterative approach. However, their algorithm may not terminate theoretically. The present authors give an optimal global SEA scheme of polynomial-time worst-case complexity.

Channel allocation pattern in a cellular communications system

Abstract: A method of allocating channels in a cellular system in which sectored base sites serve subscribers equipped with directional antennas. A plurality of available communication channels is divided into channel subsets. Base sites are arranged in clusters, and within each cluster: the number of channel subsets is equal to the number of base sites, is greater than the number of sectors per base site and is not a multiple of the number of sectors per base site; each channel subset is allocated once in each of the different sector directions; and the allocation pattern is not repeated within the cluster, whereby to minimize co-channel interference.

Multiple hyperband mobile and base stations

Abstract: According to exemplary embodiments of the present invention, multiple hyperband capable mobile stations and base stations are described. These mobile and base stations support multiple hyperband operations including, for example, mobile assisted channel allocation (MACA), mobile assisted handover (MAHO), cell reselection, traffic channel assignment, control channel location and registration. By bridging multiple hyperbands, service quality can be enhanced.

Optimal call admission to a mobile cellular network

Abstract: To fulfil the future demand for and increase the reliability of the mobile cellular service, the authors have explored the use of a call admission policy that constitutes a dynamic channel allocation scheme for a cellular system. The call admission policy optimizes a weighted blocking criteria for a queueing network model of a mobile cellular system. In this context, the call admission problem is formulated as a Markov decision process. The value iteration method has been applied to a uniformized chain of a cellular highway system. The effectiveness of a call admission policy for maximizing the call completion rate and for reducing the handoff dropping is studied. Channel reservation policies for handoffs are also examined for different system parameters. In addition, several symmetry properties of the optimal policies which effectively truncate the size of policy space, are mathematically established.

Improving the capacity in wireless networks through integrated channel base station and power assignment

Abstract: We propose a joint resource allocation algorithm (JRAA) that tries to optimise the channel base station and power assignment in a wireless network so minimising the number of channels needed to accommodate all the users in the system. We compare the performance of the JRAA, in terms of the achievable traffic capacity, with the corresponding performance of fixed and dynamic channel assignment strategies, for both the forward (downstream) and reverse (upstream) connections, and we verify the improvement of the system capacity that can be achieved by the integration of the channel base station and power assignment. Finally several versions of the two-way channel assignment problem are studied and evaluated.