05-09-2012, 01:32 PM
On Erlang Capacity of IEEE 802.16e Networks
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Abstract
In this thesis, we improve the Erlang capacity of the 802.16 OFDMA based systems. For
Erlang capacity calculation, we consider Hard as well as Soft blocking. Hard blocking is
due to finite number of subchannels in the cell and Soft blocking is due to interference
from nearby cells. Improvement in Erlang capacity is due to:
1. Subchannel permutation schemes: Permutation scheme is proposed for the sub-
channel formation, i.e., subcarrier to subchannels allocation. We have proposed a
method to reduce interference/collision of the subchannels by proposing new per-
mutation schemes. Proposed permutation scheme reduced collision by 200% for
Even-Group subchannels and 300% for Odd-Group subchannels.
2. Call Admission Control (CAC) algorithms: We have proposed power reservation
based CAC heuristic and optimal CAC algorithms in IEEE 802.16e cellular sys-
tems. For handoff calls, we use power reservation based CAC algorithm. Resources
are allocated to the user requests and then, subcarrier/subchannel are assigned to
the users. The power reservation based CAC heuristic an improvement of 58.64%
in Erlang capacity over bandwidth reservation based CAC. By using Optimal CAC,
90% improvement is observed compare to the heuristic CAC algorithm
Introduction
Background
In this chapter, we discuss the need to measure the Erlang capacity of IEEE 802.16e
cellular networks. IEEE 802.16e is the emerging technology for the near future due to
its capability to support high data rates for various application e.g. multimedia and
video conferencing. The evolution of the IEEE 802.16 standard has spurred tremendous
interest from the network operators seeking to deploy high performance, cost effective
broadband wireless networks. Several commercial implementations of IEEE 802.16e cel-
lular networks have been launched. It has also been considered as a wireless backhaul
technology for 2G, 3G, and 4G networks in both developed and developing nations.
WiMAX is a possible replacement for cellular phone technologies such as GSM and
CDMA, and can also be used as an overlay to increase capacity. This motivates us to
measure the performance of IEEE 802.16e cellular networks. The performance measure-
ment parameters to evaluate the performance of such networks can be divided into User
Centric and Network Centric performance measures.
Organization of the Thesis
The Thesis consists of 7 Chapters. Chapter 1 is an introduction of IEEE 802.16e cellu-
lar networks and performance parameters of the 802.16 OFDMA cellular networks. In
Chapter 2, we describe various permutation schemes for subchannel formation. The brief
description of related work, and their conclusions. In this Chapter we describe how the
Erlang capacity depends upon the permutation methods and its parameters. We have
formulated problem by considering all the parameters e.g., permutation sequence, IDcell
value pairs and hit-ratio of the subchnannel. Further, the effect of Inner and Outer
permutation methods is described, which is followed by solutions to the problems. Each
Section has Problem formulation and its solution with simulation results at subchannel-
ization level and scheduling level. In Chapter 3, we calculate the Erlang capacity in the
presence of hard as well soft blocking with the suffle (proposed) and existing algorithm
for the subchannelization and analysed the improvement due to proposed solution in the
Erlang capacity. In Chapter 4, we discuss CAC in IEEE 802.16e cellular networks. Var-
ious CAC strategies and resource allocation, i.e., Fixed channel allocation and dynamic
channel allocation scheme are described.
Conclusion
The optimal power reservation based CAC provides 90% improvement over the heuristic
power reservation based CAC with AMC level 5. With AMC level 3 an improvement of
25% is observed. The result of the optimal power reservation CAC is similar to Channel
Inversion.