- •1. Review of current systems for broadband wireless access
- •1.1 Comparison of key technologies WiMax and hspa
- •1.2 Comparison of the key technologies for WiMax and lte
- •1.3 Comparison of key technologies WiMax and Wi-Fi.
- •2.2 Standard 802.16: physical layer
- •2.3 Standard 802.16 Protocol mac sublayer
- •2.4 Standard 802.16: frame structure
- •In addition to the data ofdm6символ includes a guard interval duration Tg, so that the total duration of the ofdm symbol
- •3.2 Mesh network
- •3.3 Application Features multiple access ofdma
- •In addition to reviewing the methods of distribution of bearing, the standard and optional mechanisms - in particular, the so-called optional fusc, not fundamentally different from that considered.
- •3.4 Support for adaptive antenna system
- •In more detail the network architecture shown in figure 19:
- •Variant mimo with a single receiving antenna also known as the mode stc (Space Time Coding with space-time coding) and are particularly suitable in nlos conditions.
- •In turn, the values and are defined by the formulas
- •7.2 The choice of the equipment of base stations
2.3 Standard 802.16 Protocol mac sublayer
The level data is divided into three sublevels, as shown in figure 7.
Footage WT always occupy an integer number of time intervals in the physical layer. Each frame is divided into parts, the first two of which contain a map of the distribution of intervals between incoming and outgoing data traffic. There is information that is transmitted in each clock cycle, and on what beats free. Map of the distribution of the incoming stream also contains a wide range of system parameters that are important for stations that have just joined the airwaves.
The incoming traffic channel consists of a base station, which determines what to put in each part of the frame. Outgoing channel has a competing station wishing to access it. Its distribution is closely linked to the issue of quality of service. Defined four classes of services:
1. Service with a constant bit rate;
2. Service real-time variable bit rate;
3. The service not running in real-time, variable bit rate;
4. Service with a commitment apps best-effort services.
All provided by the 802.16 standard services focused on the connection, and each connection has access to one of the earlier classes of service.
Service with a constant bit rate is designed to transmit uncompressed speech, what is channel T1. Here you want to send a predefined amount of data in predefined time intervals. This is implemented by assigning each connection of this type is their intervals. Once the channel is allocated, the access time intervals is performed automatically, and there is no need to request each of them separately.
Service real-time variable bit rate used in the transmission of compressed multimedia data and other software applications real-time. Necessary in a time throughput may vary. Or that the bandwidth allocated by the base station, which polls at certain intervals of time subscriber to identify necessary at the moment the channel width.
The service not running in real-time, variable bit rate is suitable for heavy traffic - for example, to transfer large files. Here, the base station polls also subscribers quite often, but not in a strictly defined time points. The subscriber is operating with a constant bit rate, can be set in unit of one of the special bits of his frame, thereby offering a base station to interview him (that means the subscriber has data that you want to transfer with the new bit rate).
Service with a commitment to maximum effort is used for all other types of transmission. No polls here, and the station wishing to seize the channel, must compete with other stations that require the same class of service. The bandwidth request is performed at time intervals that are marked in the map of the distribution of outgoing flow as available for competition. If the request was successful, it will be noted in the following map of the distribution of the incoming stream. Otherwise, subscribers-losers must continue to fight. To minimize the number of collisions is used is taken from Еsегпеt; algorithm binary exponential rollback.
The standard defines two forms of capacity allocation: for the station and for the connection. In the first case, the subscriber station collects together all the requirements of its subscribers (for example, computers that belong to residents of the building) and provides collective inquiry. Upon receiving the bandwidth, it distributes it between users at their discretion. In the latter case, the base station works with each connection separately.