2 research outputs found
Performance evaluation of voice handover between LTE and UMTS
M.Sc.(Eng.), Faculty of Engineering and the Built Environment, 2011The main objective of seamless mobility is to enable mobile users to stay connected while roaming across heterogeneous networks. As cellular networks evolve from the third generation Universal Mobile Telecommunication System (UMTS) to the Long Term Evolution (LTE), a new Evolved Packet Core (EPC) will support heterogeneous radio access networks on the same platform. UMTS provides voice services in the circuit switched domain; while LTE operates in the packet switched domain. Cellular network operators thus face the challenge of providing voice services during initial deployment of LTE due to difficulty in mobility between the two domains. Seamless voice handover between packet switched LTE and the circuit switched UMTS network is therefore an important tool in solving this problem.
This report investigates the performance of inter-Radio Access Technology voice handover between LTE and UMTS. The schemes evaluated were Voice Call Continuity (VCC) for UMTS to LTE handover and Single Radio Voice Call Continuity (SRVCC) for LTE to UMTS handover. The performance evaluation was done using mathematical models and equations that were derived for the handover service interruption time. The resulting equations were simulated and the output was analysed and compared with the Third Generation Partnership Project (3GPP) specifications
TD-SCDMA Relay Networks
PhDWhen this research was started, TD-SCDMA (Time Division Synchronous Code
Division Multiple Access) was still in the research/ development phase, but
now, at the time of writing this thesis, it is in commercial use in 10 large cities in
China including Beijing and Shang Hai. In all of these cities HSDPA is enabled.
The roll-out of the commercial deployment is progressing fast with installations
in another 28 cities being underway now.
However, during the pre-commercial TD-SCDM trail in China, which started
from year 2006, some interference problems have been noticed especially in the
network planning and initialization phases. Interference is always an issue in
any network and the goal of the work reported in this thesis is to improve
network coverage and capacity in the presence of interference.
Based on an analysis of TD-SCDMA issues and how network interference arises,
this thesis proposes two enhancements to the network in addition to the
standard N-frequency technique. These are (i) the introduction of the concentric
circle cell concept and (ii) the addition of a relay network that makes use of
other users at the cell boundary. This overall approach not only optimizes the
resilience to interference but increases the network coverage without adding
more Node Bs.
Based on the cell planning parameters from the research, TD-SCDMA HSDPA
services in dense urban area and non-HSDPA services in rural areas were
simulated to investigate the network performance impact after introducing the
relay network into a TD-SCDMA network.
The results for HSDPA applications show significant improvement in the TDSCDMA
relay network both for network capacity and network interference
aspects compared to standard TD-SCDMA networks. The results for non-
HSDPA service show that although the network capacity has not changed after
adding in the relay network (due to the code limitation in TD-SCDMA), the
TD-SCDMA relay network has better interference performance and greater
coverage