WIMAX (Worldwide Interoperability for Microwave Access) is a mobile broadband technology, which is established by IEEE 802.16 work group. Currently it has two versions.

• 802.16d is for fixed and nomadic access, which fulfills the access of the last mile
• 802.16e is for portable mobile access, which supports roaming and handover.802.16e is an advanced and better version in terms of coverage, mobility and flexibility. The version offers whole E2E solution, seamless network architecture and convergence capability with other networks. All functions and applications of 802.16d can be provided by 802.16e.

Overview

WiMAX 16e is based on OFDMA technology which combines MIMO, AMC and HARQ to improve bandwidth and coverage.

OFDMA (Orthogonal Frequency Division Multiple Access) is a technology combining OFDM, FDMA and TDMA. Multiple user access is achieved by allocating multiple sub-channels to various users. 

MIMO (Multiple Input Multiple Output): System employ at least two transmit (Tx) antennas and at least two receive (Rx) antennas to improve the system capacity, coverage, or throughput. 

AMC (Adaptive Modulation and Coding): Based on the quality of signal, the system allocates different modulation and coding to different burst. AMC technology helps to improve the throughput of the system, supports higher transmission rate and spectrum efficiency. 

HARQ (Hybrid Automatic Repeat Request): HARQ system uses the erroneous data to extract useful information for decoding again. Comparing with ARQ, the system reduces delay of repeated transmission, and improves the coverage and capacity. 

Network Architecture

WiMAX 16e network comprises ASN (Access Service Network) and CSN (Connectivity Service Network). 

The ASN consists of BS and ASN-GW. The ASN can access multiple connectivity service networks (CSNs) and provide radio access service to CSN of different network service providers (NSPs). The ASN manages the air interface of IEEE 802.16 and provides radio access to the WiMAX subscribers. 

CSN contains network elements such as routers, AAA, user databases, and Internet gateway devices. The CSN can serve as a new network entity in a new WiMAX system or achieve the CSN functions by using the existing network devices. The CSN provides IP connectivity to the WiMAX subscribers.
 
Applications of WiMAX

WiMAX provides affordable broadband access, especially in dense urban and rural areas, where deployment of DSL and laying out cable network for broadband access is not feasible. There are five application scenarios defined in the WiMAX system, including: fixed, nomadic, portable, simple mobile, and full mobile. WiMAX network can be integrated with 2G/3G mobile networks to enrich both 2G and 3G services. Operators with 2G/3G mobile networks can thus raise their service convergence capability and enhance their overall competitive ability.