1.3 Applications of BWA

1.3 Applications of BWA

As already introduced above with IEEE 802.16, a BWA system is a high data rate (of the order of Mb/s) WMAN or WWAN. A BWA system can be seen as an evolution of WLL systems mainly featuring significantly higher data rates. While WLL systems are mainly destined for voice communications and low data rate (i.e. smaller than 50kb/s), BWAs' are intended to deliver data flows in Mb/s (or a little lower).

The first application of BWA is fixed-position high data rate access. This access can then evidently be used for Internet, TV and other expected high data rate applications such as Video-on-Demand (VoD). It will also surely be used for other applications that are not really apparent yet. In one word, the first target of BWA is to be a wireless DSL (Digital Subscriber Line, originally called the Digital Subscriber Loop) or also a wireless alternative for the cable. Some business analysts consider that this type of BWA application is interesting only in countries and regions having relatively underdeveloped telecommunications infrastructure. Indeed, using WiMAX for the fixed-position wireless Internet in Paris or New York does not seem economically viable.

Another possible use of high data rate access with BWA is WiFi Backhauling. As shown in Figure 1.4, the Internet so-called backbone is linked to a BS which may be in Line-of-Sight (LOS) of another BS. This has a Non-Line-of-Sight (NLOS) coverage of Subscriber Stations (SSs). The distinction between IEEE 802.16 NLOS and LOS technologies will be detailed in Chapter 2.

Figure 1.4: Broadband Wireless Access (BWA) applications with a fixed access. The two main applications of a fixed BWA are wireless last-mile for high data rate and (more specifically) WiFi backhauling

The SS in Figure 1.4 is a Consumer Premises Equipment (CPE). The CPE is a radio-including equipment that realises the link between the BS and the terminal equipment(s) of the user. After the CPE, the user may install a terminal such as a Personal Computer (PC) or a TV and may also connect a WiFi Access Point and then a WLAN (the BWA then realizing the WiFi network backhauling). Hence the two main applications of fixed BWA are the wireless last-mile for high data rate and (more specifically) WiFi backhauling. As shown in this figure, a wireless terminal can then be fixed (geographically) or not. This may be the case of a laptop connected to the CPE with a WiFi connection (see the figure).

The fixed access is the first use of BWA, the next step being nomadicity (see Section 1.3.1 for the difference between nomadicity and mobility). A first evolution of the SS will be the case when it is no longer a CPE but a card installed in some laptop. A nomadic access, shown in Figure 1.5, is an access where the user or the subscriber may move in a limited area, e.g. in an apartment or a small campus. This area is the one covered by a BS. Whenever the user moves out of the zone, the communication (or the session) is interrupted. A typical example of a portable access is WLAN/WiFi use in its first versions (802.11, 802.11b and 802.11a) where a session is interrupted when the terminal gets out of a WLAN coverage even if it enters a zone covered by another WLAN, e.g. in two neighbouring companies.

Figure 1.5: Nomadic or portable BWA

The nomadic access is very useful in some cases, such as campuses, company areas, compounds, etc. It can be observed that due to this position, which is not fixed, the link between the BS and the SS has to be NLOS (it can be LOS only in the case of fixed CPEs, theoretically). A nomadic access is also sometimes known as a wireless access. The final expected step of WiMAX is a mobile access. The difference between wireless and mobile will now be discussed.

1.3.1 Wireless is Not Mobile!

Different scenarios of mobility can be considered. The most simple one is when two neighbouring BSs belong to the same operator. Hence, the same billing system and customer care apply to the two BSs. In this case, a user moving from one cell to a neighbouring one has to start the session again. This feature is nomadicity rather than mobility. Mobility (or full mobility) is the scenario where the session is not interrupted, whether this is a data session, a voice communication (over IP or not), a video transmission, etc.

The distinction is made between wireless (but yet geographically) fixed access, nomadicity, portability and mobility. Portability is when a user can move with a reasonable speed over a large area, covered by many BSs, without interruption of an possible open session or communication. The value considered as a reasonable speed is of the order of 120km/h. Mobility is the same as portability but with no real limit for speed; i.e. if mobility is realised, a BWA can be used in some high-speed trains with speeds exceeding 350km/h.

In cellular systems, second generation or later, a voice communication is not interrupted when a mobile moves from one cell to another. This is the so-called ‘handover’. The cellular systems are then real mobile networks. Is WiMAX a cellular mobile network? Considering that a cell is the area covered by one BS, the only condition would be a high-speed handover feature. This should be realised with 802.16e evolution of 802.16. However, a WiMAX handover is not expected to occur at very high speeds to be precise, at speeds higher than a magnitude of 100km/h. The final objective of WiMAX is to be a mobile system. In this case, part or all of a territory or country will be covered by contiguous cells with a seamless session handover between cells, as in a cellular system (see Figure 1.6). It is evident that WiMAX will then become a rival to 3G cellular systems.

Figure 1.6: Mobile Broadband Wireless Access (BWA). A mobile WiMAX device can move over all the cells in a seamless session

Some service providers define triple play as the combination of data (Internet), voice (unlimited phone calls) and video (TV, video on demand). This evolves into quadruple play by adding mobility. In a first step, this mobility will in fact be only nomadicity, e.g. using the WiMAX subscription to have an Internet access in a caf&eU far away from home.

Another application sometimes mentioned for BWA is telemetering: using the BWA for reporting electricity, gas, water, etc. This should represent a small but yet perhaps interesting market. WiMAX telemetering products have already been reported. Evidently, WiMAX is not the only technology that can be used for telemetering.