In planning WiMAX networks, it is crucial to recognise that different types of service require vastly different levels of investment in base stations.
Even though 802.16e is commonly referred to as a ‘mobile WiMAX’ standard, WiMAX networks can be used to offer fixed or nomadic wireless broadband and voice services, as well as mobile data and voice services. However, the type of service being offered has significant implications for the capex required to provide sufficient network coverage, and it is important to fully assess all the options before starting network roll-out and launching commercial services.
Fixed and nomadic services are typically offered using customer premises equipment (CPE) that is placed near a window or exterior wall to communicate with the WiMAX network (an indoor CPE), or a CPE connected to an antenna attached to the outside of a building (an outdoor CPE). Coverage within the premises can then be provided using WiFi. Mobile services typically involve using a PCMCIA or USB device attached to a laptop, or an embedded chip in a handheld device or laptop.
As a result, the type of service offered has direct implications for the depth of coverage required. Fixed or nomadic services only require that the WiMAX signal penetrates the first wall of the customer’s building. Mobile data services require good depth of coverage, including penetration deeper inside buildings. Mobile voice services – which would be offered in competition with existing mobile operators – require more ubiquitous coverage nationwide, with good in-building penetration. In addition, devices used for mobile services have lower transmitting power than indoor or outdoor CPEs.
These different coverage levels require vastly different investment in base stations. This is particularly the case for WiMAX, given the relatively unfavourable propagation and building penetration properties of the 2.3GHz, 2.5GHz or higher frequencies typically allocated to WiMAX operators. Analysys Mason has performed an indicative analysis of the number of base stations required to cover a hypothetical city of 1000 square kilometres using 2.5GHz spectrum, depending on the type of CPE used and the depth of coverage provided. This is illustrated in Figure 1.
Figure 1: Numbers of WiMAX base stations required to provide different levels of coverage across a 1000km2 city using 2.5GHz spectrum [Source: Analysys Mason]
This analysis calculates the minimum number of base stations required simply to provide coverage. In a real network deployment, additional base stations would be required to provide enough capacity to serve customers.
It can be seen that the number of base stations, and therefore capex, can vary significantly depending on the type of coverage required. A fully mobile network, using PCMCIA cards attached to laptops, with one-wall in-building penetration requires more than double the number of base stations compared to a fixed or nomadic broadband network using indoor CPEs. With two wall penetration, the number increases to almost four times that of a fixed wireless network. This has major implications for the decisions a WiMAX operator needs to make on service offerings and roll-out plans.
A fully mobile network, while able to provide services which may compete with those offered by existing mobile networks, will come at a much higher cost than a more focussed network which initially only offers fixed services. WiMAX network operators therefore need to carefully consider the balance between potential revenues and capex when deciding on service offering.