IJETAE_1111_03

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, Volume 1, Issue 1, November 2011)

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Review of congestion control algorithms for Performance Evaluation of WCDMA

Arnika khare1, Prof. Yudhisthir Raut2

1 M.Tech Scholar, Department of Electronics And Communication, NIIST, Bhopal, M.P. India

2 Department of Electronics And Communication, NIIST, Bhopal, M.P. India

[email protected]

[email protected]

Abstract — WCDMA is an important air interface

technologies for wireless networks. As WCDMA based

cellular networks fully developed, the current point-to-

point links will evolve to an IP-based Radio Access

Network (RAN).This Paper present a review of congestion

control mechanism using Router control, channel control

and admission control method for IP-RAN on WCDMA

cellular network. The Router control mechanism uses the

features of WCDMA networks using active Queue

Management technique to reduce delay and to minimize

the correlated losses. The Random Early Detection Active

Queue Management scheme (REDAQM) is to be realizedfor the router control for data transmission over the radio

network using routers as the channel. The channel control

mechanism control the congestion by dividing the access

channel into multiple layer for data accessing. Call

Admission Control (CAC) is one of the important

methods in the performance evaluation of cellular

network of Wideband CDMA. CAC handles different

classes of users and type of services. It is the most

highlighted part and deals with the resource allocation

and resource management. The aim of this paper is

improve and enhance the quality of service by generating

different congestion control algorithms for multiclass

users

Keywords — Call Admission Control (CAC), Wideband

Code Division Multiple Access (WCDMA), Radio access

network (RAN), Active queue management (AQM),

Random Early Detection Active Queue Management

(REDAQM).

I. I NTRODUCTION

Cellular wireless networks have become an

important part of the communication infrastructure. It

has been selected for implementation in both the North

American and European 3G standards. Traditionally, in

these wireless access networks, the base stations are connected to radio network controllers or base station

controllers by point-to-point links. These links, also called backhaul links, are expensive and their use

impressive an ongoing cost on the service providers. In

such networks, reliability comes at a high price: by

replication of links or controllers.

IP RAN has the following advantages:

Cost : Point-to-point links, including T1 links, are

expensive and cannot be shared. An IP network will

benefit from statistical multiplexing gains and could be

shared with other wireless and wireless applications.

Scalability and Reliability: Replacing point-to-point

links by a distributed IP network will provide alternate

paths to more than one network controller, thereby

improving reliability and scalability. For example, it is

shown in [2] that adding a selected few paths between

base stations and network controllers results in the

majority of the gains in resiliency to failures.

Data Applications: Increasingly, a large number of IP

based “data applications,” including Web browsing,

email, streaming, and packetized voice (voice over IP)

are being offered in wireless networks. Hence, wireless

access networks must support IP traffic. An IP RAN

efficiently addresses this eventuality.

mailto:[email protected]






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Fig.1. Wireless Access Network with IP RAN.

While the use of an IP RAN results in the aboveadvantages, mechanisms must be designed to control IP

RAN congestion. Congestion occurs when the offered

traffic exceeds the IP RAN capacity. There are

essentially three approaches to control and avoid

congestion:

1.CALL ADMISSION CONTROL: In WCDMA cellular

network bandwidth is varying over time due to inter

and intracell interference. To overcome the scarcity of

bandwidth in WCDMA, CAC is used. It is the rule to

admit requested calls maintaining the quality of service.

CAC is basically to make a decision about whether a

user should be admitted into the system according to

the users’ quality of service requirements and the

current traffic load.

Fig.2: Flow chart for CAC algorithm

2. ROUTER CONTROL USING ACTIVE QUEUE

MANAGEMENT : Active queue management (AQM)

[4] is a form of router control that attempts to provide

congestion control by monitoring the congestion state

of a router queue and proactively dropping packets

before the buffers become full and queuing delays

become too high. Some of the AQM policies (e.g., [7])

drop packets with a certain probability to avoid bursty

loss.

Y

N

Y

N Robust

N Fragile

N

Fig.3 active queue management

3. DIVERSITY CONTROL: Diversity allows mobile

users to smoothly transition their connections from one

cell to the next without loosing connectivity or

suffering service degradations as is typical in hard-

handoff scenarios. Diversity control selectively

discards uplink voice radio frames from potentially

redundant secondary legs for some mobile users at the

base stations in such a way that the voice quality is not

noticeably degraded while reducing traffic in the IP

RAN to manage congestion. Key challenges in

diversity control are the service degradation and

restoration policies, which dictate how users are chosen

for and freed from diversity control, respectively.

New flow

Calculate avg & maxq

Non adaptive?

Minth<avg<maxth

Avg<minth

Dro tail

Drop

RED

Accept

New state

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In this paper, the work done in [3] is analyzed and

the future work will be to implement the same analysis

but with artificial intelligence. The rest of the paper is

organized as follows. Section II is a brief on literature

reviews of the related topics. Section III describes the

future scope with the conclusion in section IV.

II. LITERATURE SURVEY

To satisfy ever-increasing demands for higher data

rates, as well as to allow more users to simultaneously

access the network, interest has peaked in what has

come to be known as wideband code division multiple

access (WCDMA). And WCDMA is packet switched

network. An important issue in packed switched

network is congestion. In this section we discuss the

survey Of various congestion control mechanism.

Several papers are published with the impact of

congestion.

Many algorithms have been proposed for the CAC

for wireless CDMA cellular networks. In fact, this topic

is among the interest of many of the researchers.

Several papers are published with the CAC algorithm

where handoff is given priority. That is certain

bandwidth is reserved for the handoff calls also known

as guard channel policy [8, 10, 11]. Researchers have

been done in this field based upon the SINR (signal to

interference and noise ratio) calculations [12], [13]. Butin these literatures, the mobility of the user has been

kept constant. And also, the channels are not assumed

to be dynamic in nature due to which there is under

utilization of the resources when the load is not so

heavy. In paper [9,14], imperfect power is assumed to

determine the SIR. in [15] assumed the imperfect

power, dynamic channel allocation and imperfect

power. In [16], used packet switched MC-CDMA

supporting multimedia applications in which handoff is

given priority developing the CAC based on real time

measurements by estimating the effective bandwidth in

the users’ cell and the neighbouring cells too for the

mobility information. The simulation achieved low new

call blocking and handoff call dropping probabilities. In

[17], the CAC algorithm is proposed which considers

not only the cell in which the call is originating but also

neighbouring cells so that the handoff call blocking

probability is reduced. Shen, Chang et all [18] proposed

intelligent call admission controller with fuzzy logic

theory to estimate the new and handoff call interference

based on the knowledge of effective bandwidth

method. They say that intelligent system such as fuzzy

logic or neural network system cope up with the traffic

uncertainty. According to their paper, the fuzzy logic

system is preferred when there is no mathematical

model of a process. Random early Detection is one of

the active queue management control mechanism

deployed at gateways [1]. The RED gateway detects

incipient congestion by computing the average queue

size (Jacobson, 1998). The gateway could notify

connections of congestions either by dropping packets

arriving at the gateway or by setting a bit in packet

headers. When the average queue size exceeds a preset

threshold, the gateway drops or marks each arriving

packet with a certain probability, where the exact

probability is a function of the average queue size.

RED gateways keep the average queue size low whileallowing occasional burst of packets in the queue.

In[19] presented the WCDMA networks, radio

network controller (RNC) is a potential bottleneck for

TCP connections - due to difference in available

bandwidth between the core network (CN) and the

radio access network (RAN). This may result in packet

data convergence protocol (PDCP) buffer overflows or

excessive delays at the RNC, as PDCP buffers are

flow-specific. In order to avoid PDCP buffer overflows,

different active queue management (AQM) methods

may be applied at the RNC. In typical cellular

networks, mobiles can be in SHO with up to six base

stations at once with one primary leg and up to fivesecondary legs. These multiple legs constitute what is

known as the mobile’s active set. Field measurements

(also corroborated by [5] and [6]) indicate that CDMA

voice users tend to operate in SHO mode almost half of

the time, with an average of about 1.5 legs per call. In

[10] diversity control exploits traffic redundancy, it can

be a very effective congestion control technique by

adapting to congestion without either increasing the

frame error rate or blocking.

III. FUTURE SCOPE

The implementation makes few assumptions for the

implementation of the two control mechanisms such asidle channel equal speed traffic balanced, burstiness

etc.These assumptions hold well during algorithm

evaluation but may deviate in its operation in real time

scenario. An effort could be made to evaluate the

performance considering these factors also. The

proposed implementation is evaluated on apart of

image and speech sample, an effort can be made to

speed up the operation of this implementation in future.

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The algorithm can also be tried out with other

communication system such as MC-CDMA, CSCDMA

etc. The implementation can also be evaluated

considering various channel parameters for real time

evaluation .these implementation could be made to

evaluate the performance of mobile ad-hoc network.

IV. CONCLUSION

The evolution of wireless communication for multi

bit rate application has come down to integration of

different technologies for efficient transmission of data

over wireless network. In this paper, we studied the

problem of congestion control in the IP RAN of a

WCDMA wireless access network and examined three

control techniques, called admission control, diversity

control, and router control. This paper, review of

different types of call admission control algo. is done.

The aim of this research is to enhance the same

algorithm with multiclass and multiservice user this

paper realizes the two most advanced congestion

control policies namely the Channel Admission Control

and Router Control controlling in wireless network. For

the evaluation of control algorithms a wireless network

with WCDMA standard is adapted. A router interface is

described as an intermediate interface between the

source and destination to provide better services using

an IP- enabled wireless. This algorithm is designed an

incorporated with router architecture for the control of congestion at early stage. The controlled is achieved by

floating the congestion level between minimum and

maximum threshold.

References-

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[3] K. Maney, “Future Not So Bright for Telecoms,” USA Today,

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