Network Management In Wimax

Published Date: 02 Nov 2017

Network and Information Security

Kingston University

Kingston upon Thames, UK.

[email protected]

Abstract

Wimax is referred to as a last-mile broadband option; it was based on the IEEE 802.16 standard to provide long range broadband wireless services which Wifi couldn’t provide.

Wimax has been rolled out in areas that have no infrastructures to connect to traditional PSTN telephone services, areas that are considered rural and remote, and therefore remain unserviced by major telephone companies. Network management in Wimax coverage areas as to do with how network resources are shared and allocated to wide range of customers over a wider gap, due to the fact that the Wimax technology enables more coverage and increased internet speeds at greater distances from the base station.

For purpose of this paper, Network management would deal with how network resources are utilized to achieve the best quality of service and to establish an optimum number of users per coverage area without corresponding loss in service delivery.

Keywords include: Wimax, PHY, MAC, ARPANET, INTERNET, IEEE, 802.16

1.0 Introduction

Internet connectivity has increased from former figures to a more outstonishing levels in recent years. With the advent of the internet in pre-1994[1], when ARPANET [2] as the internet was then known as communication exchange between schools and government institutions in the United states and along the line, a move to increase the number of root servers, meant internet connection could be routed and other countries like England, china, Russia and some European countries join the internet by means ocean connecting fibre to interlink and have considerable presence on the internet.

From the advent of the 21st century, many other least developed countries are making big in-roads to the World Wide Web or internet, to establish a global presence and to be accessibility by the world over, making the term a global village a necessity.

As more countries have internet connectivity, the rate of internet access penetration has increased dramatically and has used up all known connection means traditionally known. The increase has been growing steadily from cable to DSL, to ADSL, to Dialup modem, to Vsat dish, to Fibre, then lastly to Wireless. The rate of internet penetration compared to the world human population is still low and more people needs to be serviced or connected to the internet, as from various research carried out in previous years, many people depend on the internet to work, connect with family and live.

As technology advanced from wire to wireless LAN, more devices have capable interface (i.e. 802.11 b/g/n cards) that can be used to access the internet and as such, previous interface are limited to a few metres from an access point and do not provide mobility or portability over distances, therefore the IEEE 802.xx standard committee in 2004 [3] began developing a new standard and birthed the Wimax standard (802.16a)[4] to be like the Wifi, but with longer reach and availability to accommodate many users at a time.

2.0 What is Wimax?

Wimax is a wireless technology standard based on IP addressing services and it is a standard of choice in implementations a Metropolitan Area Network (MAN). Wimax has evolved to be service of choice to deliver unparallel network services to wider range of people over a large geographical spread, the Wimax standard is based on the IEEE 802.16a committee work arising from the limitation of the 802.11 standard families. The aim of the Wimax committee group is to bring broadband access to a wider range of people with a minimal setup by interpolation of 802.11 standards wifi with Wimax to provide end to end connectivity.

Wimax can also be referred to as wifi over long distance, as this feature allows for 802.11 hop spots connection and also provide broadband access wireless alternative to DSL and cable connection. Of the use in which Wimax can be applied to includes provision of VOIP services, to real-time multimedia streaming and it can easily be integrate into a GSM /3G mobile network enabling telecommunications service providers an edge to give their subscribers better performance and seamless broadband service at minimal cost.

2.1 Network management in Wimax network

For effective control in Wimax technology, the 802.16 standard specify two layers which are PHY (Physical Layer) and MAC (Media access control layer). These, two layers enable network management and control in Wimax, through critical examination of how they are implemented and how they interpolate to give a robust structure and performance.

2.1.1 The Physical layer (PHY)

The IEEE 802.16 working standard group in their 2012 report specified that the frequency band of choice lies between the 10 – 66 GHz band and this is to allow telecommunication companies to deploy and optimize their network in respect to cell planning, radio capabilities and capacity. [5]

In the PHY layer, the frequency spectrum in use is based on the type of modulation used, which can be FDD and TDD multiplexed, using this modulation scheme(FDD & TDD) their framing sequence allows for burst transmission in relation to one of the IEEE requirement for Wimax system operation. The framing techniques in use communicating between the base station(BS) and the mobile subscriber (MS) should supports adaptive burst profiling which is based on the type of modulation and the coding schemes used subject to the mobile subscriber unit (MS) ability to support either full-duplex or half-duplex transmission rate.

The PHY sub header frame allows for Uplink (UL) and Downlink (DL) transmission, while the UL allows for both TDMA and DAMA, its regulated to slots division to provide services such as MS registration, contention rate, guard bits to help in authorization and authentication with the BS to allow provision of network access. The DL uses only the TDM multiplexing is used and allows for service with the number of competing MS to receive streams of data within a particular sector or beam width of the propagating antenna.

2.1.2 The Media Access Layer (MAC)

For effective connection and provision of network service, the MAC layer has to function. It does this by providing a connection –oriented service by mapping the service from the BS to the MS with varying levels of QoS parameters. After a new entrant in form of a MS enters, it registers and requests for connection and the BS assigns a service flow to act as a reference guide to further bandwidth request. This type of connection defines the kind of transport mechanism needed when MS changes or moves, and it also define the connection and the convergence process between peers that uses the MAC and utilize a service flow. [6, 802.16-2012.pdf, 6.1]

The Wimax architecture defines a connection oriented approach through service flows and schedule service to provide a QoS assurance in the architecture.

2.1.2.1 Scheduling service

For network request and subsequent service by the BS, every MS is assigned up to [7] 3 dedicated CIDs of 16-bits size (Connection Identifier) to allow for management data to be sent and received on those CID channels. QoS rules apply, to the transmission and receiving of the management data. Before any data connection is allowed on a Wimax network, allocation of CID must occur, then the asking party or MS sends a connection requirement to the BS; the BS sets an appropriate connection using service flow and scheduling service [8] The scheduling service manages the poll and grant procedure between the two units (MS & BS) and to meet the QoS requirements, 5 main scheduling services are define to satisfy this requirements before data can be served to the recipient (MS) over an air channel.

The 5 scheduling services are Unsolicited Grant Service (UGS), Real-time Polling Service (rtPS), Extended Real-time Polling Service (ertPS), Non Real-time Polling Service (nrtPS) and Best Effort (BE).

a) The unsolicited grant service is a service that deals with providing for real-time service request that require fixed size data traffic periodically to service an application (e.g. VoIP, IPTV...)

b) The real-time polling service is to provide variable packet or data size depending on the application being served periodically. (E.g. video or audio streaming)

c) The extended real-time polling service is based on the combination of the UGS and the rtPS service, to provide real-time services for applications that generate variable packets or send out data traffic per time in a particular order or manner. It functions to provide dynamic allocations of data traffic.

d) The non-real time polling service allows for packet transmission of non real-time events like mail and other applications that don’t require constant and heavy bandwidth allocation.

e) The best effort has no throughput or latency issues, as it passes the network traffic in a random format subjected to load characteristics at the MS unit end.

Table 1 —Scheduling services and usage rules

Scheduling

Type

Piggyback Request

Bandwidth

stealing

Polling

UGS

Not allowed

Not allowed

PM bit is used to request a unicast poll for bandwidth needs of non-UGS connections

rtPS

Allowed

Allowed

Scheduling only allows unicast polling

nrtPS

Allowed

Allowed

Scheduling may restrict a service flow to unicast polling via the transmission/request policy; otherwise all forms of polling are allowed.

BE

Allowed

Allowed

All forms of polling allowed

2.1.2.2 Service flows

For a particular QoS level, the service flow functions in one direction only with respect to the flow of packet, and there are 3 three basic types of service flows discussed below:

Provisional service flow: - this function like a deferred service is usually provisioned but not activated for use until the MS choose to activate the function by sending to the BS, an SFID and the associate QoS parameters.

Admitted service flow: - this uses a two stage activation method to function, thereby ensuring all necessary connection requests are satisfied and completed before allowing access to the MS from the BS serving it.

Active service flow: - this is a form of service flow that is provisioned and activated immediately. This process is available after authorization and mostly a faster form of the admitted service flow, in which the two-stage activation is skipped.

2.1.3 QoS Concept

From the 802.16e-2012 standard, ‘the QoS concept is itemised in 3 ways, which are: a) Service flow QoS scheduling, b) dynamic service establishment and c) two-phase activation model’. The operations relating to the concepts are related to the UL and DL traffic between the ms and the BS. To satisfy the QoS provision, the following must be met to give end-to-end QoS assurance.

They are: 1) An MS should be preconfigured to allow a configuration and registration function in line with the QoS service flow and traffic functions.

2) A signalling function has to be in place for QoS service flows and traffic function.

3) Scheduling of the MAC header and the QoS traffic function for UL service flows.

4) Utilization of QoS traffic data for the DL service flow must be setup.

5) Service flows connection originating from the ms connecting to the BS needs to be grouped into definite class to support upper-layer entities or applications that may request connection based service flow with a desired QoS functions in a consistent way. [9]

2.2 Network management in Wimax subset network

In a proposed subset Wimax network, different network entities interact to provide a seamlessly service and often interface the connection process between the MS and the BS. In a development network, such sub entities like the RS, MR, MR-BS exist and help to provide service to the competing MS or several users at the same time. In order to manage traffic and service each user effectively, the MR-BS controls the relay of flow control messages from the RS which is in form of DL traffic, it uses the REG-REQ/RSP to indicate whether DL control is enabled or not. When a flow control is enabled within a MRS-cell or subset, the MBS performs independent flow control on each traffic from each competing RS requesting connection.

The DL flow control happen in two states: which are the controlled and the uncontrolled state. The uncontrolled state, means traffic can be sent in an uncontrolled manner to the SS/MS. However, in the controlled state, the recipient tells the BS what amount of data or packet it can receive per time.

Bandwidth and throughput allocation are however dependent on the number of users within a particular subset and the ability of each competing SS/MS can meet up with the BS QoS level before connection can be made and adjusted to reflect each connection characteristics and data required to service any particular application running on the SS/MS at any particular time.

3.0 Conclusion

For effective management of Wimax networks, sending a large file from a peer to another peer would mirror the way the entire connection works and from the analysis of the transfer would give us a view as to how [10] throughput and latency and also the required bandwidth to send that particular file from one point to another. This transfer option shows the type of service flows that should be best used and the most appropriate scheduling service to achieve a high level of QoS measurement in a Wimax sub network, and when compared to the whole network and which each subset adequately tested, the overall performance of the Wimax network can be evaluated and assessed in terms of delays, latency, bandwidth issues, maximum capacity per antenna or sub-network and the type of protocols or application that can be supported without loss of service at any point.