1. University of Tehran
College of Engineering
School of Electrical and Computer Engineering
Thesis Title:
Capacity Analysis in Hybrid Wireless Networks
By: Hakimeh Purmehdi
Advisor:
Dr. Farshad Lahouti.
A thesis submitted to the Graduate Studies Office
in partial fulfillment of the requirements for
the degree of M.Sc. in
Communication Engineering
September 2009

2. Abstract
With the increasing number of cellular subscribers and their demand for multimedia
services, new wireless network architectures are being planned for the near future. Employing ad
hoc communication mechanisms within cellular networks, lead to improved performance for the
resulting hybrid networks. The design and performance analysis of such networks have attracted
much attention during the recent years. Ad hoc communication techniques may be employed to
extend the coverage area, reduce the interference level or manage traffic heterogeneity in cellular
networks.
Ad hoc relaying can be employed in a cellular network in two different ways. First, mobile
terminals can play the role of ad hoc elements by forwarding the data of certain users toward
other users or a base station. Alternatively, in some proposed models, there are dedicated relays
acting as ad hoc elements within the network. Enjoying less constrained power resources, and a
suitable physical location, dedicated relays achieve better link quality in comparison with mobile
users.
In this thesis, the performance of hybrid wireless networks with dedicated relays is
investigated. Two hybrid network models, for load balancing and interference reduction, are
introduced. Dedicated relays wirelessly connected to base stations are positioned at the border of
adjacent cells. Taking analytical approaches for the introduced hybrid network models, the
probability of blocking and the probability of outage is obtained, which demonstrate the
effectiveness of the proposed hybrid solutions. Also, a signal to interference ratio call admission
control (SIR-CAC) scheme for a hybrid CDMA network is analyzed. Numerical results verify
the extensive gain obtained by employing ad hoc relaying over the conventional CDMA
networks in the presence of SIR-CAC. Moreover, simulation results are provided, which
illustrate the excellent accuracy of the presented analytic approaches.