Performance
of
Broadcast
and
Multicast
Service with Interference Cancellation
业
! I Based on
Macro
Diversity
Zhang
Yumei
1
Sheng
YU
2
1 China Unicom National Engineering Laboratory
of
Broadband Service Applications, Beijing
100032
, China
2 China Unicom Research Institute, Beijing
100048
, China
Abstract
The cdma2000 lxEV-DO mob
i1
e communication system provides broadcast and multicast services (BCMCS)
to meet an increasing demand for multimedia data services.
Single
企
equency
network (SFN) is recognized as an effective
way to improve the spectral effìciency
of
the BCMCS system.
To
improve the
coverag
巳
and
the data rate
of
the BCMCS
users
, an interference cancellation algorithm based on macro diversity is introduced in this paper. The performance
of
BCMCS in CDMA2000
EV-
DO networks under the condition
of
SFN
is
evaluated. The simulation results show a significant
improv
巳
ment
in bit error ratio (BER) wh
i1
e quantitatively validating the effìciency
of
our approach
Ke
沪
Nords
CDMA2000 l
xE
V-DO Systems; Broadcast and Multicast Services (BCMCS); Single Frequency Network (SFN);
Interfì
巳rence
Cancellation; Macro Diversity
1 INTRODUCTION
As the mobile communication systems evolve into the
third generation
, the focus has shifted away from voice
services and on to data services. Reliable
deliv
巳
ry
of
files
of
all sizes simultaneous to many users over unreliable and
bandwidth-limited networks is an
extrem
巳
ly
challenging
tas
k.
It
has been recognized that broadcast networks must be
used for the effìcient distribution
of
such conten
t.
Recen
tI
y,
work has begun in both the Third Generation Partnership
Project (3GPP) and the 3GPP2 on enhancing 3G networks
to support multimedia broadcast and multicast services. In
WCDMA
, a
ml
丑
ultimed
副
ia
broadcast and
r
口
m
丑
mltic
凶
ast
s
臼
er
凹
Vlωc
巳
(MBMS)[lυl
卜山
.2
气
2
specification for a
cdma
旧
a2000
hi
毡
ghι1
卜
-rat
臼巳
broadcast
pa
肌
cket
data air
int
旬巳
rfa
创
ce[
口
3μ
叫-4
1
.
Their goal is to design a system which
can deliver multimedia broadcast and multicast traffìc with
minimum resource usage
by
both radio access and core
networks. With the rapid development
ofthe
broadcasting, a
special network structure called Single Frequency Network
(SFN)
is
proposed. In the SFN, all
th
巳
transmitt
巳
rs
broadcast
181
信息通信技术
the
identical
information
simultaneously
at
the
same
企
equency.
Therefore high spectrum effìciency
is
,也
e
major
advantag
巳
of
the
SFN[5
1
. One implementation
of
the
SFN
is utilizing identical cell scrambling code for all the cells
in the SFN area. The other
is
cell-specific scrambling code
using chip combining to receive. Since BCMCS content is
likely to be ava
i1
able through a large part
of
the network,
macro diversity is a natural choice to improve coverage and
enable higher data rates. 3GPP release
6[6
1
introduces two
macro diversity schemes: soft and selective combining.
In the SFN, the received signal can be seen as a mixture
of
multiple
delays
of
the
transmitted
signals.
In
the
traditional
SFN
scheme, the time dispersion,
including
the so-called "artificial" multi-path propagation caused by
the SFN structure and the receiver
, is usually mitigated
by
equalization[7
1
.
Considering
the
received
signal
is a
superposition
of
the
signals
coming
from
quite
a few
transm
Ït
ters in
SFN
,
if
one
or
several
transmitters
are
shadowed
, others are still receivable. This characteristic
resu
Its in
the
possible
diversity
gain.
The
multi-user
detection research area covers many different algorithms
for
mitigating
interference
among
users[
町,
which
can