WiMAX Point-to-Multipoint and Mesh Network

In Point-to-Multipoint (PMP) mode, a single-hop network contains a central unit as a Base Station (BS) to makes decision to the entire nodes such as Subscriber Station (SS) within its cell that is a central geographic entity of a cellular structure.

In a mesh network, a number of SS are not in direct contact through the BS where a relay system is necessary on intermediary SS that resolve relay information toward other SS that are not in direct contact with the BS.

WiMAX MAC Layer

One of the important aspects of WiMAX is the MAC layer supports more than one physical layer (PHY) mode. This characteristic not only enable companies to differentiate their product from each other, but also makes WiMAX to be an adaptive technology that can suit special requirements depending on application.

The WiMAX MAC layer performs the standard function of providing a medium independent interface to the PHY layer. The major focal point of the MAC layer is handling resource of air-link proficiently.

MAC layer is responsible on the whole connection to arrange packet transmission among multiple Point-to-Multipoint (PMP) and mesh network models.

The MAC layer is separated into three sub layers. There are called specific convergence sub layer (CS), MAC common part sub layer (CPS), and the security sub layer.

The MAC CS support asynchronous transfer mode (ATM) service and packet service used for packet-switched networks. The MAC CPS provides utilities to facilitate both types of service in the CS.

The security sub layer is the third sub layer within the MAC layer. It is designed for privacy, authentication, and confidentiality used for the SSs in the network.

The MAC is capable to grant differentiated service to users on the equivalent medium throughout a range of method. MAC design plays an essential role in WiMAX networks. A MAC protocol defining rules for orderly access to the physical shared medium is vital when it comes to efficient utilization and fair sharing of resources to desired system performance such as high throughput and short delay.

Reduce Scanning Time and Optimization of Ranging Process in WiMAX Network Entry

Reduce the channel scan approaches during the scanning time are able to achieve a fast scanning process but this approaches may not guarantee Subscriber Station (SS) to acquire a precise information for the purpose of association with Base Station (BS).

While optimization of ranging process may improve the connection but it will sometimes disregard the performance of WiMAX network traffic flow.

WiMAX

What are we know about WiMAX?

1. WiMAX bandwidth must be shared among multiple users and affect the speed in practice.
2. WiMAX is similar to WiFi but in can enable usage at much greater distances.
3. The Asia Pacific region has surpassed the North American region in terms of 4G broadband wireless subscribers.
4. WiMAX is the most energy-efficient pre-4G technique among LTE and HSPA+.
5. Throughput between clients and base station determined largely by distance.

Long Channel Scan and Collision in Ranging Process in WiMAX Network Entry

How the effect of long channel scan and collision in ranging process during scanning to ranging steps in network entry is managed? One method is by 'reduce scanning time' and another one is 'optimization of ranging process'.

Reducing scanning time approaches have had success in reduce a number of channels to scan so that fast scanning is achieved while optimization of ranging process approaches was appealing in term of optimizing the connection probability and average connection delay.

Other approaches also exist such as to upgrade the IEEE 802.16 protocol performance regarding the delay during subscriber network entry process, analyzing the collision probability and analytical modeling of network entry process.

Most of the approaches are primarily focused on modification of scanning and ranging procedure. All of these approaches correspond to the IEEE 802.16 standard but most of them are not easily implemented and ignored the ability of WiMAX system parameter setting. Most of them also not considered to implicate with better communication system's QoS for WiMAX network.

The overview of these approaches has shown that while they may be relevant for the associated environments, they do not provide solutions that could help in both process of scanning and ranging in WiMAX network entry. The question is, what is the appropriate technique that can be used to relate the specified process of scanning to ranging in network entry that can deal with the problem of long channel scanning and collision in ranging process?

Scanning to Ranging Problem during WiMAX Network Entry

The problem during scanning to ranging steps in network entry will degrade the access time for initialization and recovery of service in WiMAX network. For example, a lengthy channel scanning will causes a service disruption between the SS and BS. The collision in ranging will lead to disconnection between SS and BS.

As part of functionalities mechanism for network entry in MAC CPS, this could result unexpected delay and under utilization of WiMAX link.

One way to manage the delay during scanning to ranging steps is by evaluating the WiMAX network entry system parameter setting.

Most of the current approaches are too focused on scanning and ranging process and has ignored system parameters setting that can influence scanning to ranging steps delay in network entry.

Network Entry Process of WiMAX MAC CPS

Network entry process is part of MAC CPS sub layer. It is the first step for Subsciber Station (SS) joining the WiMAX network. It referred to the early procedure SS perform to register themselves with the Base Station (BS) that controls the 802.16 network.

There are several steps associated with network entry as following:

• Scanning to ranging.
• Intersection of SS's and BS's capabilities.
• Authentication and authorization.
• SS registration and connection establishment.

WiMAX MAC CPS Functionalities

The main functionalities of WiMAX MAC CPS are:

1. Network entry.
2. Connection management.
3. Quality of Service (QoS) control.
4. Air-link control
5. Protocol Data Unit (PDU) operation.
6. Mobility and power management.
7. Multicast and broadcast service.

The MAC CPS provides the fundamental MAC funtionality of system access, bandwidth allocation, connection establishment, and connection maintenance.

The MAC management messages are part of MAC CPS component. The IEEE 802.16 standard defines three types of connection for each messages those are broadcast connection messages, basic management connection messages, and primary management connection messages.

WiMAX IEEE 802.16 Standard

The worldwide Inter-operability for Microwave Access (WiMAX) is a telecommunication  technology based on IEEE 802.16 standard. WiMAX supports two types of network topologies which is Point-to-Multipoint (PMP) and Mesh. In the PMP, the link connection is only between Base Station (BS) and Subscriber Station (SS).

The standard was designed to evolve with media access control (MAC) layer consists of three sub layers. The three sub layers are:

1. Service specific convergence sub layer (CS)
2. MAC common part sub layer (CPS)
3. Security sub layer