Mobile WiMAX is expected to deliver significant improvements over Fixed WiMAX which makes it even more attractive for fixed deployments. In wireless environments, link budget (measured in dB) and spectral efficiency are the two primary parameters used for evaluating system performance. Listed below are some of the improvements in link budget and/or spectral efficiency achievable by Mobile WiMAX which are equally applicable to fixed deployments:
• Convolutional Turbo Coding, Hybrid-Automatic Repeat Request (HARQ) and Frequency- as well as Time-Selective Scheduling adds up to 10 dB to the link margin, significantly increasing cell radius and spectral efficiency (bits per second per Hertz).
• Antenna techniques such as MIMO and AAS2 can deliver almost a 50% improvement3 in spectral efficiency over SISO/SIMO implementations as well as link budget improvements.
• Additional improvements to spectral efficiency and the support of users with different QoS come from the use of a two-dimensional (frequency and time) channel aware resource scheduling as well as interference cancellation at the devices.
• Additional reduction of the control overhead is enabled by the use of compressed MAP info.
• Use of sub-MAPs enables the base station to optimize the link to subscribers based upon their location, e.g., whether they’re at the cell edge or close-in.
• Mobile WiMAX uses TDD (Time Division Duplex) as its duplexing mechanism which provides significant benefits for asymmetric data flows:
i. By their nature, FDD systems have symmetric DL and UL channel allocations. TDD allows the operator to vary DL vs. UL allocations. For example, by using a 3:1 DL to UL ratio instead of a symmetric, 1:1 ratio, the DL data rate can be increased by more than 50%.
ii. Because the same channel is used for UL and DL for TDD, it allows for more efficient channel estimation which aids MIMO & AAS techniques.
• Efficient utilization of bandwidth for multicast/broadcast services, and power savings by implementing sleep/idle modes.
• The OFDMA-based air interface is designed to combat inter-cell interference by appropriate resource allocation in different cells.
Note that typical multi-cell deployments can use a frequency re-use scheme of one: 1 (cluster) x 3 (number of sectors) x 1 (number of frequencies in the cell). This scheme results in the most efficient use of spectrum.
Performance Advantages of Mobile WiMAX
Wireless Acces Point (WAP)
Definition: Wireless access points (APs or WAPs) are specially configured nodes on wireless local area networks (WLANs). Access points act as a central transmitter and receiver of WLAN radio signals.
Access points used in home or small business networks are generally small, dedicated hardware devices featuring a built-in network adapter, antenna, and radio transmitter. Access points support Wi-Fi wireless communication standards.
Although very small WLANs can function without access points in so-called "ad hoc" or peer-to-peer mode, access points support "infrastructure" mode. This mode bridges WLANs with a wired Ethernet LAN and also scales the network to support more clients. Older and base model access points allowed a maximum of only 10 or 20 clients; many newer access points support up to 255 clients.
ISDN (Integrated Services Digital Network)
ISDN is a telephone system network. the phone system was viewed as a way to transport voice, with some special services available for data. The key feature of the ISDN is that it integrates speech and data on the same lines, adding features that were not available in the classic telephone system.ISDN allows multiplexing of devices over single ISDN line
ISDN is a circuit-switched telephone network system, that also provides access to packet switched networks, designed to allow digital transmission of voice and data over ordinary telephone copper wires, resulting in better voice quality than an analog phone. It offers circuit-switched connections (for either voice or data), and packet-switched connections (for data), in increments of 64 kbit/s. Another major use case is Internet access, where ISDN typically provides a maximum of 128 kbit/s in both upstream and downstream directions (which can be considered to be broadband speed, since it exceeds the narrowband speeds of standard analog 56k telephone lines). ISDN channels may use bonding to achieve a greater data rate, typically 3 or 4 BRIs (6 to 8 64 kbit/s channels) are bonded.
In a broad sense ISDN can be considered a digital communications medium existing on layers 1, 2, and 3 of the OSI model. ISDN is designed to provide access to voice and data services simultaneously.
(a)Types of channels:
1. Bearer channel (B-channel=64 kb/s) clear pipe for data
2. Delta channel (D-channel, 16 kb/s or 64 kb/s) call signaling information:
o who is calling
o type of call
o calling what number
(b) Service types:
1. Basic Rate Interface (2 B channels + 1 D channel (16 kb/s))
2. Primary Rate Interface (30 B channels + 1 D channel (64 kb/s))
1. Basic Rate Interface:
o Digital data exchanged between subscriber and NTE - Full Duplex
o Separate physical line for each direction
o Pseudoternary coding scheme
o 1=no voltage, 0=positive or negative 750mV +/-10%
o Data rate 192kbps
o Basic access is two 64kbps B channels and one 16kbps D channel
o This gives 144kbps multiplexed over 192kbps
o Remaining capacity used for framing and sync
2. Primary Rate Interface:
o B channel is basic user channel
o Data
o PCM voice
o Separate logical 64kbps connections for different destinations
o D channel used for control or data LAPD frames
o Each frame 48 bits long
o One frame every 250ms 
Applications:
Typically supporting PBX
[1] 1.544Mbps
o Based on US DS-1
o Used on T1 services
o 23 B channels plus one D channel
o Line coding is AMI using B8ZS
[2] 2.048Mbps
o Based on European standards
o 30 B channels plus one D channel
o Line coding is AMI using HDB3 
(d)Characteristics:
o Speed(160 kb/s for BRI & 2048 kb/s for PRI)
o Fast call setup(2 Seconds)
o Bandwidth on Demand
o Bandwidth on Demand(adding new channels to the bundle of channels)
o Multiple devices phone(fax, PC, videoconferencing system, router, terminal adapter,.. each with its own sub-address)
WiMAX receiver (or Customer Premises Equipment - CPE)
The technical term for customer premise equipment (CPE) is subscriber station. The generally accepted marketing terms now focus on either “indoor CPE” or “outdoor CPE”
4.2.1 Outdoor CPE
.
Outdoor CPE, very simply put, offers somewhat better performance over indoor CPE
given that WiMAX reception is not impeded by walls of concrete or brick, RF blocking
glass or steel in the building’s walls. In many cases the subscriber may wish to utilize an outdoor CPE in order to maximize reception via a line of sight connection to the base station not possible with indoor CPE. Outdoor CPE will cost more than indoor CPE due to a number of factors including extra measures necessary to make outdoor CPE weather resistant.
4.2.2 Indoor CPE
The most significant advantage of indoor over outdoor CPE is that it is installed by the
subscriber. This frees the service provider from the expense of “truck roll” or installation.
In addition, it can be sold online or in a retail facility thus sparing the service provider a
trip to the customer site. Indoor CPE also allows a certain instant gratification for the
subscriber in that there is no wait time for installation by the service provider. Currently,
many telephone companies require a one month wait between placement of order and installation of T1 or E1 services. In addition, an instant delivery of service is very appealing to the business subscriber in the event of a network outage by the incumbent service provider.
4.2.3 Power Factor
The device is an integrated Ethernet and AC/DC power supply adapter that simply plugs into a standard electrical wall outlet (110/240 VAC).
Overview of AirSpan WiMAX Base Station Products
Airspan provides three families of WiMAX Base Station;
1.HiperMAX,
2.MacroMAX and
3.MicroMAX.
These all support Mobile and Fixed WiMAX profiles across various frequency bands and have individual characteristics suited to particular deployment types as follows:
HiperMAX - Highly flexible WiMAX base station for high availability services.
HiperMAX is a dual mode (802.16d and 802.16e) macro-cell base station with a split indoor / outdoor architecture designed to support multiple transceiver smart antenna techniques. It is a base station solution optimised for supporting high availability WiMAX services through various levels of system element redundancy.
MacroMAX - Integrated macro-cell WiMAX base stations.
MacroMAX is a family of single mode (802.16d or 802.16e) highly integrated macro-cell base stations with all-in-one packaging of RF and baseband components. MacroMAX includes integrated dual RF transceivers to support two channel diversity and MIMO. It is available as an all outdoor solution for Mobile WiMAX applications to minimise physical footprint and operator OPEX and an all indoor solution for Fixed WiMAX applications.
MicroMAX - Integrated micro-cell WiMAX base stations.
MicroMAX is a family of single mode (802.16d or 802.16e) highly integrated micro-cell base stations with all-in-one outdoor packaging of RF and baseband components. For Mobile WiMAX applications, MicroMAXe includes integrated dual RF transceivers to support two-channel MIMO. Performance optimised variants for high density rooftop deployments and cost optimised variants for low density / rural deployments are available in a variety of frequency bands.
Mobile WiMAX End to End Network Architecture
Figure (1) illustrates the WiMAX Network Reference Model (NRM,) consisting of the following logical entities: MS, ASN, CSN and clearly identified reference points for interconnection of the logical entities. The figure depicts the key normative reference points R1-R5. Each of the entities, MS, ASN and CSN represent a grouping of functional entities. Each of these functions may be realized in a single physical device or may be distributed over multiple physical devices.
Fig. 1 WiMAX Network Reference Mode
Access Service Network (ASN)
The ASN defines a logical boundary and represents a convenient way to describe aggregation of functional entities and corresponding message flows associated with the access services. The ASN represents a boundary for functional interoperability with WiMAX clients, WiMAX connectivity service functions and aggregation of functions embodied by different vendors. Mapping of functional entities to logical entities within ASNs as depicted in the NRM may be performed in different ways. The WiMAX Forum is in the process of network specifications in a manner that would allow a variety of vendor implementations that are interoperable and suited for a wide diversity of deployment requirements.
Connectivity Service Network (CSN)
Connectivity Service Network (CSN) is defined as a set of network functions that provide IP connectivity services to the WiMAX subscriber(s). A CSN may comprise network elements such as routers, AAA proxy/servers, user databases and Inter-working gateway devices. A CSN may be deployed as part of a Greenfield WiMAX Network Service Provider (NSP) or as part of an incumbent WiMAX NSP.
DEPLOYMENT SCENARIOS OF WIMAX
WiMAX can potentially be deployed in a number of scenarios depending upon the requirements, financial considerations and need of supported services. The following subsections discuss the most probable scenarios in detail.
A. Wireless Backhauling :
Until now, wired backhaul had been the prevalent form of backhaul due to an abundance of wired technologies. Heavy investments had already been made into laying down cables and other infrastructure. With the advent of WiMAX, operators have a cost-effective and high-performance alternate to traditional backhauling technologies. The robust bandwidth
B. LOS based wireless broadband access:
Last-mile broadband technologies, such as WiMAX, shall accelerate the deployment of 802.11 hotspots and Small Office Home Office (SOHO) wireless LANs. By allowing TSP’s to
on prevailing requirements. For the same reasons, 802.16-d can be used to serve remote and under-served areas with low population densities where traffic can be cost-effectively
C. Mobile Wireless Services:
With the proliferation of 802.11 hotspots, users will naturally want to be wirelessly connected, even when they are outside the range of the nearest hotspots. The 802.16-e flavor
