Chapter 2: WiMAX Genesis and Framework

2.1 IEEE 802.16 Standard

The main features of IEEE 802.16/WiMAX technology are the following:

(Carrier) frequency <11 GHz. For the moment, the frequency bands considered are 2.5 GHz, 3.5 GHz and 5.7GHz.
OFDM. The 802.16 is (mainly) built on the Orthogonal Frequency Division Multiplexing (OFDM) transmission technique known for its high radio resource use efficiency.
Data rates. A reasonable number is 10 Mb/s. Reports have given more ambitious figures going up to 70 Mb/s or even 100 Mb/s. These values would be for a very good state of the radio channel and for a very small cell capacity, making these values too optimistic for the moment.
Distance. Up to 20 km, a little less for indoor equipments.

As mentioned in Chapter 1, the IEEE 802.16 standard is the network technology used for WiMAX. The IEEE 802.16 working group for BWA was created in 1999. It was divided into two working groups:

802.16a, centre frequency within the interval 2–11 GHz. This technology will then be used for WiMAX.
802.16, with a frequency value interval of 10–66 GHz.

Many documents were approved and published by 802.16 subcommittees. They are presented in Table 2.1.

Table 2.1: Main IEEE 802.16 documents
Open table as spreadsheet
Date and name of the document	Description
Dec. 2001, 802.16	10–66.GHz; line-of-sight (LOS); 2–5 km; channel bandwidth values: 20, 25 and 28 MHz
Jan. 2003, 802.16a	2-11 GHz; non-line-of-sight (NLOS)
Oct. 2004, 802.16-2004	Revises and consolidates previous 802.16 standards; replaces 16a and 16; 5–50km
7 Dec. 2005, 802.16 approves 802.16e amendment of 802.16-2004	Mobility; OFDMA (SOFDMA)
Other 802.16 amendments approved or at draft stage: 802.16f, 802.16g, 802.16f, etc.	See Section 2.5

As stated in 802.16-2004 ^[1], this standard revises and consolidates IEEE standards 802.16-2001, 802.16a-2003 and 802.16c-2002. Before getting to 802.16-2004, a revision called 802.16d was started in September 2003 with the objective of taking into account the ETSI HiperMAN BWA standard ^[3]. The 802.16d project was later concluded with the approval of the 802.16-2004 document and the withdrawal of the earlier 802.16 documents, including the a, b and c amendments. Confusingly enough, some people still refer to 802.16-2004 as 802.16d (or even 16d).

2.1.1 From 802.16-2004 to 802.16e

802.16-2004 was definitely very useful, replacing a set of documents all describing different parts of the same technology, with different modification directions. Yet, after its publication, it still needed an upgrade, mainly for the addition of mobility features. Other features were needed and some errors had to be corrected. This gave way to 802.16e amendment approved on December 7, 2005 and published in February 2006 ^[2].

It should be noted that 802.16e is not a standalone document. It only proposes (sometimes important) changes and additions to the 802.16-2004 text. Hence, a person wishing to read the details of specific information in 802.16, e.g. ‘What is the frame format in 802.16?’ has first to read the related part of 802.16-2004 and then go on to read the possible changes that took place in 802.16e. It was reported that the IEEE intention was to have a unique document resulting from 16-2004 and 16e fusion, called 802.16-2005. However, by summer 2006, this document does not exist (to the best of the author's knowledge). However, the 802.16-2004 standard and 802.16e amendment are sometimes referred to as the IEEE 802.16-2005 standard.

The main differences of 802.16e with regard to 802.16-2004 are the following (the list is not exhaustive):

Mobile stations (MS) appear. A station in a mobile telecommunication service is intended to be used while in motion or during halts at unspecified points. However, a 802.16e MS is also a subscriber station (SS).
MAC layer handover procedures. There are two types of handover (see Chapter 14).
Power save modes (for mobility-supporting MSs): sleep mode and idle mode (see Chapter 14).
SOFDMA (Scalable OFDMA). More generally, the OFDMA PHY layer, i.e. Section 8.4 of the 802.16 standard, was completely rewritten between 16-2004 and 16e. Although the word SOFDMA does not appear in the 802.16e document, it is the type of standardised OFDMA. For OFDMA and SOFDMA, see Chapter 5.
Security (privacy sublayer). The security of 16-2004 is completely updated (see Chapter 15).
Multiple-Input Multiple-Output (MIMO) and Adaptive Antenna System (AAS) techniques, both already introduced in 802.16-2004, have many enhancement and implementation details provided in 802.16e (see Chapter 12).
Multicast and broadcast services (MBS) feature.
A new (fifth) QoS class: ertPS. (In addition to 802.16-2004 rtPS), ertPS Class supports realtime service flows that generate variable-size data packets on a periodic basis, e.g. VoIP with silence suppression.
Other: the Low-Density Parity Check (LDPC) code is an optional channel coding, etc.

^[1]IEEE 802.16-2004, IEEE Standard for Local and Metropolitan Area Networks, Air Interface for Fixed Broadband Wireless Access Systems, October 2004.

^[3]Wikipedia, the free encyclopedia, http://www.wikipedia.org.

^[2]IEEE 802.16e, IEEE Standard for Local and Metropolitan Area Networks, Air Interface for Fixed Broadband Wireless Access Systems, Amendment 2: Physical and Medium Access Control Layers for Combined Fixed and Mobile Operation in Licensed Bands and Corrigendum 1, February 2006 (Approved: 7 December 2005).