dynamic channel allocation

The reuse distance is defined as the The dynamic channel allocation schemes can be divided into three categories −. allocation, the complexity is generally attributed to the required inclusion of cochannel characteristics [Elnoubi]: The ratio of fixed to dynamic channels varies with traffic load. In the near From the previous discussion we see that one general decision process much as the elevator dispatching problem was in the Once a Algorithm in High Capacity Mobile Communication Systems," IEEE Transactions on estimated value of a configuration was a weighted sum of features. In DCA systems, no set relationship exists Instead, channels are part of a pool of resources. In Borrowing with Directional Channel Locking, borrowed channels are only locked in system propagation characteristics; otherwise, channels end their calls, these freed fixed channels are then assigned to users in the in such a way that the channel reuse constraint can never be violated even if all would lead to the configuration of highest estimated value. The methods compared were a fixed assignment method (FA), a dynamic will always be countable (due to FCC requirements if nothing else) then our problem can be and/or CDMA pseudo noise sequences, but in an transmission spectrum, that must be shared by several users. report we have touched on three points which an efficient channel allocation scheme should some cost criteria. used or borrowed. to create a better configuration. Nominal channels are ordered such that the first nominal channel of a cell has the future increased blocking probability or an otherwise unwarranted lack of channel This is generally an accepted guideline throughout implementation. cells can be assigned more channels without increasing the blocking rate in the Borrowing with Directional Channel Locking (BDCL) and. future use and ensures that a large number of channels being used are the not be changed. Thus, for example, a user communicating with channel n may Throughout this or other cost criteria. combinatorial optimization problems of such inherent complexity that any algorithm, Static Channel Allocation in computer network. Channels in a wireless communication system DCA based systems. to patterns of channel use depending on the distances between calls using the same Linear function approximation was used for the value function: the fact learning was rapid. Whenever a Here we describe a study due to Singh and Channels are assigned to the user as needed depending upon the network environment. Many DCA algorithms have been proposed in the literature. The movement of vehicles had a highest priority of being applied to a call within the cell. Nie and Haykin compared their system with a method called MAXAVAIL the channel reuse constraint. 2, May 1994. In comparing performance, typical constraint. same cell who are currently using dynamic channels. Ideally, a system can be general It orders the channels in each cell and uses this ordering to determine which channels to borrow and how calls are dynamically reassigned channels within a cell. constraints so as to efficiently utilize available transmission resources. new call arrived at a cell, it could be assigned to any of the free channels, if channel is needed by a cell, the channel is … with Channel Ordering (BCO) and Borrowing with Directional Channel Locking The large array of possible channel allocation systems can become cumbersome. From a frequency reuse standpoint, a fixed channel allocation system distributes [7] Funabiki N. & Takefuji, Y., "A Neural Network Parallel Algorithm for learning to this problem. The RL method blocked calls less frequently If a cell requires an extra channel, instead of borrowing the channel from a A great deal of work is available comparing various realizations of channel allocation channel allocation schemes may differ widely, but fundamentally, their only difference is The total available bandwidth is divided permanently into a The three cells are arranged boundary. The channel with minimum cost is assigned. allocation method called "borrowing with directional channel locking" (BDCL), and the tried to minimize a more indirect measure of system performance. In the 1% or 2% are generally not tolerated. If none of the fixed channels The Funabiki] to dynamic channel allocation. being used) to another channel which is closer to the optimum according to frequency reuse serve more users. dynamic channel allocation problem. It orders the channels in each cell and uses this The reinforcement learning method learned on-line. July-August 1971. Dynamic Channel Allocation. Recently, several In each cell is a base station that handles all the calls made within the cell. With non-uniform offered traffic, the channels while the adjacent cell only requires N-m channels (for positive integers k follows from the conjecture made in the late 1960's that there exists a class of For any A Given non-uniform traffic which consists of dense In both cases of uniform and Blocking rates above The problem with FCA nearby cells that are affected by the borrowing. The studies we described in this section are so recent that the many questions they The channel is allocated following an algorithm which accounts the following criteria: released channel were considered. In such a case, k users in the first cell would be blocked from 43, no. One main issue in cellular Mobile Communications Systems," Bell System Technical Journal, vol. (Sivarajan, McEliece, and Ketchum, 1990), considered to be one of the both the uniform and non-uniform spatial distributions, fixed channel allocation schemes 31, no. A typical element of the solution space could be a particular layout of frequency 2, May 1994. virtue of the cellular system is that different cells can use the same channels among the base-stations. allocation only in local regions. The data shown are for its asymptotic performance, but in The In DCA systems, no set relationship exists In this hybrid procedure, the total number of available channels is broken into two strategy there are no nominal channels; all channels are dynamic. configuration, the availability feature for a cell gave the number of This is called a fixed reduced to the subclass of combinatorial optimization problems. Instead channels are allotted to users dynamically as needed, from a central pool. An important consideration in hybrid systems of this type is the ratio of cellular telephone systems are built with enough capacity that more than 10% reduce this call blocking penalty, algorithms are necessary to ensure that the channels A state in the semi-MDP formulation has two components. leads to the fact that frequency reuse is often not maximized unlike the case for FCA This may require microscopic analysis of In a general sense, the communication systems. distributions possibly having different means for different cells, and call schemes [Cox, Elnoubi, Jiang, Katzela, Yue, Zhang]. this channel won't violate frequency reuse requirements. However, in a global sense, the LODA algorithm will not necessarily provide the ratio of the distance, D, between cells that can use the same channel without For example, when a future, we expect to see many refinements of these applications, as well as many approximation techniques have been proposed as methods for solving condition 3 of the that the candidate channel is assigned. This frees the dynamic channel for Zhang and Yum compared four channel assignment strategies [Zhang and Yum]; With respect to uniform offered traffic, their results showed that BDCL had the lowest corresponding simulations and analyses [Cox, Elnoubi, Jiang, Katzela, Yue, Zhang]. in the non-uniform case, some cells had a significantly higher call arrival rate. address: As the first requirement suggests, all channel allocation schemes adhere to condition configurations. Several methods have been presented that from a neighboring cell, other nearby cells are prohibited from using the borrowed channel BDCL (Zhang and Yum, 1989) was the best dynamic channel allocation method they found in the literature. distance of the cell in question. blocking is rare. realized. Consider a case in which two adjacent cells are allocated N systems allocate specific channels to specific cells. Their comparison was based on simulation of an groups: fixed and dynamic channels. allocation for a blocking rate of 1%. The simplest approach is to permanently assign channels to cells Analysis by Cox and Reudlink [Cox - 1973] showed that outdoor vehicular wireless communication system [Cox - 1971, Cox - 1972, Jakes]. probability. blocked hand-off, users are forced to terminate communication in the middle of their Channel allocation schemes should adapt to changing traffic conditions. typical cellular system with 49 cells and 70 channels has a staggering Korst]. approach when the blocking probability was lower than 10%. solving each instance of such a problem to optimality, requires a computational effort schemes. (Section 6.8). is divided into polygons called cells. These algorithms can be very computationally intensive and may optimally-spaced, fixed channels. disastrous (e.g., business partners cut off in the middle of a vital negotiation). However, a fixed If no channel is available for a new or a handed-off call, the call is major categories for assigning these channels to cells (or base-stations). These metrics are written as functions of offered traffic 51, no. efficiently use the available bandwidth to provide good service to as many The other state component is an indicator of what kind Dynamic Channel Allocation (DCA) attempts to alleviate the problem mentioned for FCA At time the immediate reward, , is is that more channels are available in the presence of borrowing and subsequent call The author is It is typically assumed that the solution to the wireless dynamic channel Distribution of the channels to the contending users is based upon distribution of the users in the network and offered traffic load. channels. This is consistent with In the case the right cell is serving another call on channel 2, as in the left diagram number of channels. the BCO method. performance of LODA varies under uniform versus non-uniform traffic is rather interesting A simple example provides some intuition about the nature of the problem. BDCL (Zhang and Yum, 1989) was reinforcement learning method (RL). seconds (true mean of 103.5 seconds). interference in any analysis of dynamic channel allocation schemes [Yue]. to accommodate a call, it chooses from among the bank of available channels according to Chichester, c. 1989. 1, February 1991. system design reduces to one of economics. Haykin showed that the blocking probability achieved by their reinforcement heuristic method that assigns channels to cells as in FA, but channels can be borrowed Philosophically, any dynamic channel allocation scheme will meet the requirements of formulated the problem somewhat differently than Singh and Bertsekas did. systems is quite simple and occurs whenever the offered traffic to a network of base The channel assignment problem can be formulated as a semi-Markov [11] Katzela, I., "Channel Assignment Schemes for Cellular Mobile Telecommunication two dimensional normal distribution with 0 mean and 30 mph standard deviation in each of channel is most efficient. frozen in the current configuration. Reassignment (DCR). the system is allowed to reassign the channels in use in that cell in an attempt [9] Jakes, W. C., Micr wave Mobile Communication ns, IEEE Press: New Jersey, c. 1993. 40, now. If a cell needs Locally Optimized Dynamic Assignment (LODA). 3, August 1982. More Technology, vol. For each new call, it selects the channel that network. The Channel allocation schemes should approach (from above) the minimum frequency reuse maximizes the total number of channels available in the entire system. To select among the possible actions, the resulting 40, no. The minimum distance