Worldwide Interoperability for Microwave Access
WiMAX is a wireless broadband communication technology that uses an OFDMA modulation scheme and IP networking and data transport protocol. The standards implemented for mobile WiMAX deployment are IEEE 802.16e-2005 and WiMAX Forum Network Working Group specification. WiMAX provides fixed and mobile wireless broadband connectivity with a base station without a direct line-of-sight connection with BS. WiMAX is therefore an alternative for wired T1 or DSL broadband connection.
WiMAX Network Components
The main functional components of the WiMAX network are described as follows:
Mobile Station – Fixed/Mobile Station is the Customer Premise Equipment that connects to the Base Station on the R1 reference point. BS is an interface between mobile users and ASN.
Base Station – The Base Station (BS) provides wireless connectivity through the R1 interface to the Mobile Station (MS). R1 is the reference point between MS and BS that implements IEEE 802.16e-2005 standards. The resource allocation for uplink and downlink connection between BS and MS, traffic classification and service flow management is performed by the air link scheduler that resides in the Base Station.
Access Service Network – ASN constitutes Base Stations and ASN Gateways. CSN complements the ASN IP functionality. ASN performs IP forwarding and radio-independent control plane authorization, authentication and accounting (AAA), security and mobility functions. AAA agent or Home Agent resides in CSN and allocates the IP address for the Mobile Station. When a data packet arrives on a Home Agent it is tunneled to ASN. The data packet is either sent out on the radio link to the Mobile Station or inter-ASN mobility may occur. Policy and QoS info for a subscriber resides in ASN and is applied in service flow creation.
Speed and Range
The IEEE 802.16 WiMAX standard was defined for the 10 to 66 GHz range. The IEEE 802.16e-2005 standards use Scalable Orthogonal Frequency Division Multiple Access (SOFDMA) and Multiple-Input Multiple-Output (MIMO) communication to support multiple antennas for full mobility support. WiMAX delivers a data rate of 40Mbps in a cell radius of 3-to-10 kilometers and is therefore used to provide T1 and DSL connections to businesses and residences respectively. WiMAX thus bridges the gap between rural and urban broadband speed requirements with multiple 256Kbps to 2Mbps DSL connections and 1.544 Mbps T1 connections.
WiMAX equipment must pass the interoperability tests and conformance with ‘profiles’ provided by WiMAX Forum. The WiMAX IEEE 802.16-2004 chipset for fixed wireless connection is used in Customer Premise Equipment (CPE) devices to support a group of subscribers, desktop modems and notebooks. Many firms are developing the 802.16 PHY and MAC components and software for WiMAX chipset. The PHY and MAC components are included in CPE and BS. The system profiles that are implemented on WiMAX devices provide the information about the modulation scheme supported, frequency range, channel frequency step, sampling factor, cyclic prefix, frame length, channel control parameters, receiver parameters supported, security policies implemented, e.g., PKM version implemented, authorization policy supported, etc.
Comparison with 3G
3G is a mobile phone standard that provides a 5-10Mbps data rate. The 3G technology is based on ITU standards International Mobile Telecommunications (IMT-2000). The comparison between WiMAX and 3G technologies is given in the table below:
|Technology||Fixed and mobile WiMAX,||UMTS, HSPA, 1x EV-DO|
|Standards||IEEE 802.16-2004 & IEEE 802.16e-2005||3GPP, 3GPP2|
|Speed||Up to 46Mbps||Up to 14.4 Mbps|
|Range||1-5 miles||1-3 miles|