論信道分配有效利用的策略
導讀：這篇dissertation從細胞形態、利用距離、切換概念以及蜂窩網絡中的動態信道分配幾個方面進行論述，從而為如何有效利用信道分配提供解決方案。本dissertation由英國dissertation網的留學生dissertation代寫頻道整理提供。
Introduction:
one channel per call, two channels per call, allocation of single channel or multiple channels，The resources utilization depends upon the traffic types and allocation scheme. The concept of channel allocation in wireless communication network provides a detail over view of the channel allocation schemes that I am using for cellular network. Channel allocation schemes provide understanding of need to create cells inside a wireless network.

The Cell shape:
We have Spread spectrum limitations. Hexagons shape cell are introduce to avoid large interference between users of different applications. nodeB in each cell provides air interference.

To overcome Co-Channel Interference (CCI) all the Channels are allocated in a way that they try to cancel the interference of adjacent cell in the networks. Here the concept of frequency reuse comes into account.

Reuse Distance:
The ratio of distance 'D' between the centers of co-channel cells for example in figure:3.1 the distance From "A to A" is "D" and the single cell radius 'R' of the network and is denoted by q.

Handoff Concept
Channel Allocation:
In current channel allocation schemes, we have fixed IEEE 802.16d and mobile IEEE 802.16e for cellular systems. This scheme used CDMA, CDMA-2000 in UMTS with WiMAX. IEEE 802.16d scheme we can accommodate fixed Users like banks, office locations in a cell, on the other hand we have dynamic position mobile IEEE 802.16e users. Depending on their requirements these IEEE standards allocate permanent or temporary channels it means users with fixed IEEE 802.16d,there is no need of handovers. To minimize the rate of call drop engineers purpose different channel allocation schemas in which RCS for handovers is well known I this chapter we will simulate the pros and cons of NPS and RCS.

Channel allocation strategies like FCA, DCA and HCA are very much in use. Wireless broadband technology force us to provide blocking less system to certain users we need to provide fixed channels (permanent channels). It is better to use both FCA and DCA schemes together (HCA) where traffic is high.

Dynamic Channel Allocation In cellular Network
1.probabilities of blocking (Pb)
2.handover failure (Ph)
3.forced termination (Pft) and,
4.not completed calls (Pnc)
In channel allocation part based on I have proposed two channel allocation schemes, No Priority Scheme and Reserved Channel Scheme, simply known as NPS and RCS respectively. These are handover schemes Reserved Channel Scheme (RCS) is prioritized handover scheme and No Priority Scheme (NPS) is non-prioritized handover scheme. These schemes were previously used for Personal Communications Service (PCS) says.#p#分頁標題#e#

No Priority Scheme (NPS):
It has following dynamics.

1.FIFO scheme based.
2.Each cell have same priority it means Non-prioritized.
3.no reserved channels for handoff and emergency calls also no permanent channel allocation to accommodate fix users.
4.Blocking probability and handover failure can be partially control by DCA of channels.
5.NPS scheme is better for those cells with low traffic intensity, so that blocking probability may never occur.
6.DCA scheme is used when we have high traffic in NPS.
Reserved Channel Scheme (RCS):
It has following dynamics.

1.Dynamic to give priority to every function.
2.Functions like call attempts, handovers and permanent channel allocation.
3.Highest priority is for permanent channel allocation, then for handovers and then for call attempts.
4.Permanent channels and reserved channels for handovers can be implemented using FCA and remaining channels using DCA.
5.Helping network to reduce probabilities of blocking (Pb),handover failure (Ph),forced termination (Pft) and, not completed calls (Pnc)
Analytical Method for NPS and RCS:（英國dissertation網http://www.400190.com/）
We will try drive the Blocking Probability, handover failure, forced termination and not completed calls . These probabilities are defined as:

Blocking Probability (Pb):
Probability that incoming call is block due to unavailable channel is called Pb. In such a case user will be rejected.

Handover Failure Probability (Ph):
Probability that an ongoing connection dropped due to all channels busy condition in neighboring cell is called Ph. In other words new call arriving in the cell is dropped due to unavailability of a channel in that cell (handover failure).

Forced Termination Probability (Pft):
Already accepted call is terminated due to handover failure, after a successful handover to the neighboring cell. Pft is not an actual parameter as it depend on Ph.

Probability of Not Completed Calls (Pnc):
This is the probability of all the calls that were not completed because of any one of the three scenarios i.e. call blocking, handover failure, forced termination due to handover failure.

Parameters description:
New call attempts and handover arrivals in the cell follow Poisson distribution. Channel occupancy time is distributed exponentially. Channel occupancy is defined as the time for which channel is occupied for a call or handover call process).

Here in the cell
Call Arrival Intensity
Handover call arrival intensity
Handover call Departure Intensity
Permanent call Arrival Intensity
Permanent call arrival intensity is constant because they are fixed. Mobile user arrival intensity and handover arrival intensity may change. Service intensity for handover call is and for cell with no handover is.#p#分頁標題#e#

In it is considered that if total number of servers is , then total probability is given by Pj. In fixed IEEE 802.16d and mobile IEEE 802.16e we have an additional parameter which is Permanent call arrival intensity, represented by. This parameter will have no effect on NPS.

NPS Analysis
In NPS all users have same priority on channels availability in the cell. We consider that s is the total available number of channels. The channel will be granted if there is free channel in s.

RCS Analysis
In RCS, scenario for RCS we assume that we have total channels out of which h channels are reserved for handover purpose and channels are for permanent allocation.

REFERENCES:
1.Toni Janevski, "Traffic Analysis and Design of Wireless IP Networks" Artech House
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3.TLTE3040 TeleTrafic Theory,University of Vaasa,2008,Lacture 3
4.Kleinrock, L., Queuing Systems Volume I: Theory, New York: John Wiley & Sons, 1975.
5.Lam, D., D. C. Cox, and J. Widom, "Teletraffic Modeling for Personal Communications Services," IEEE Communication Magazine, Vol. 35. No. 2, February 1997.
6.L. O. Guerrero, A. H. Aghvami, "A Prioritized Handoff Dynamic Channel Allocation Strategy for PCS," IEEE Transactions on Vehicular Technology, Volume 48, No. 4, JULY 1999.
8.Muhammad Rehan Usman,Johar Iqbal,Fahad Razzaq, "PERFORMANCE ANALYSIS OF CHANNEL ALLOCATION SCHEMES IN WIMAX," Blekinge Institute of Technology November 2009
9.Jaana Laiho and Achim Wacker, Tomas Novosad, "Radio Network Planning and Optimisationfor UMTS" 2006 John Wiley & Sons Ltd
10.David Tse, Pramod Viswanath, "Fundamentals of Wireless Communication" Cambridge University Press 2005
11.Jon W.Mark Weihua Zhuang , "Wireless Communications and Networking", 2003 by Pearson Education.Inc.
12.Roger FreemanFundamentals.of.Telecommunications.2nd.Edition.Apr.2005
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