This section presents some specific aspects related to the planning of access networks to provide wireless broadband service such as WiMAX, LMDS, WiFi, etc. These networks consist of a point-multipoint system where stations cover an area with N possible fixed users.
The planning process is based on common steps specified in the section on access network planning, although some aspects are presented here to better adapt to networks.
Then, steps of access network planning process are listed, highlighting in each of them, and when necessary, the points to which the user must pay special attention in these networks planning.
NEEDS ANALYIS - CONFIGURATION
•Cartography. This technology requires practically ensure the line of sight existence between the transmitting and receiving stations. For that, it is important to have a very detailed cartography that may differ depending on the service area for the network, requiring in each case rural, urban cartography or both.
When the stations are located in rural areas terrain models are usually between 50 and 5 meters resolution. The terrain models have values of terrain levels above sea level, so it do not contemplate presence of buildings or vegetation. In order to ensure the correct behavior of the network in an extreme case, it is possible to use a morphographic layer and to introduce certain height increments depending on areas of vegetation or buildings.
In urban areas, where buildings can obstruct direct ray between stations, it is advisable to use terrain models with buildings at 1 or 2 meter resolutions.
When stations are located in proximity to urban nucleus, it is possible to use multiple layers of altimetry to analyze propagation towards the interior taking into account obstacles like buildings.
•Calculation methods. Most wireless broadband technologies such as LMDS, WiMAX, etc. operate at frequencies above 2 GHz and often require line of sight or minimal diffraction losses in path obstacles for proper operation.
oThe Xirio Line of Sight method estimates free space losses of a path as long as it is clear of obstacles.
oIn cases where technology allows signals reception in presence of obstacles along the way, urban diffraction methods can be used, where accurate urban cartography is available, or common diffraction methods such as ITU-R Rec. 526 or Deygout method in rural environments.
Finally, if morphological layers are available, it may be useful to increase levels on certain types of terrain, such as vegetation or urban areas. In this way it is possible to take into account the hypothetical presence of obstacles in the path that are not reflected in the terrain digital model.
•Link balance. Before network planning, the user must perform their link balance calculation and determine the critical path between uplink and downlink. Because the path losses are identical in both directions, Xirio simulates only the downlink. However, if the user detects that the uplink is the critical path, he can simulate it by simply exchanging the power and sensitivity parameters of the Base Station and the Client Station in the transmitter and radio reception parameters.
•Stations and sectors. Mobile communications networks are typically composed of a stations distribution in a cellular mesh. Each station can consist of one or more sectors. The way to define these entities in Xirio is to define a site as the transmitting station location and as many transmitter as sectors.
•Best server by signal. The user has to give the criteria that Xirio will use to determine the desired sector (best server) at each location. This will be the sector to which the mobile would be linked at every location in normal conditions. The usual approach is to work with a better server by signal, that is, the mobile would be linked to the transmitter which provides the highest signal level.
•Receivers Orientation. It is important to note that receivers linked to each coverage study automatically orient their antenna towards their associated transmitter in the coverage study. When the receiving antenna is directive, this aspect is important since its associated transmitter signal level has maximum gain of the receiving antenna while the other signals are attenuated from other azimuths.