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Distributed antenna system is a distributed in a building, dedicated to form a plurality of antennas for wireless indoor coverage network. Such a system can be either an active system or a passive system.
Folding active DAS and passive DAS
A passive DAS system is a network of coaxial cables, couplers and power dividers (used to distribute RF signals to antennas in buildings). Passive DAS systems use leaky coaxial cables instead of discrete antennas. The use of leaky coaxial cables or the use of discrete antennas usually depends on the building structure and installation conditions.
Active DAS system usually adopts optical signal distribution technology, by a local interface unit converts the RF signal into optical signal RBS. These optical signals and then through the cable distribution to a plurality of remote units, the remote unit then convert them back to the RF signal. Small antenna or coaxial cable distribution network connected to each remote unit, used to cover every floor.
Passive DAS system has many advantages compared with other systems. For example, passive DAS system has lower initial input and higher reliability. Especially when the arrival of the 3G, as a kind of broadband system, passive DAS solution is also very suitable for the use of multiple operators and multiple business systems, including all types of wireless services, such as wireless LAN trunking mobile communication system, the cellular system and the rate of up to 2.5GHz (WLAN). Due to the different buildings, each region for wireless broadband coverage requirements are different, the passive scheme can according to the coverage requirements of different buildings, respectively, regional coverage of different systems, to avoid a massive loss for non selective coverage and power system. Because of this, most of the existing complex indoor coverage systems are passive DAS solutions.
Advantages of folding DAS system
The DAS system provides a base station indoor than small and distributed for operators (slightly RBS) more effective indoor coverage solution. For example, it can increase the number of relays, the wireless interface and the transmission link so that each wireless link in building any available. This, in turn, improves spectrum efficiency and enables operators to cope with traffic peaks. RBS only needs one transmission line to cover the whole building. This not only greatly improves the transmission relay efficiency, but also reduces the transmission overhead of each RBS. In addition, DAS solutions for operators to control and limit the coverage within the building, in order to reduce mutual interference with the macro cellular network, thereby increasing the total capacity of the network.
In addition, DAS is an efficient solution to provide indoor coverage for WCDMA. In this solution, multiple buildings or indoor areas share the same RBS. The RBS with an optical signal distribution system is connected, which is responsible for converting the RF signal into optical signal through the optical fiber, then these signals are assigned to each building. High power optical remote unit each within the building responsible for converting the optical signal back to the RF signal, and then through a coaxial cable antenna network signal distribution to the building in every. The deployment of DRS solutions include: by increasing the number of relays to increase capacity, reduce the transmission cost, reduce the investment cost of the wireless access network.
In addition, DAS solutions can increase the number of relays for wireless interfaces and transmission links, thereby improving spectral efficiency, since each wireless channel is readily available in each related building. Not only that, but also the full capacity of RBS can be used in any building or place, allowing operators to cope more easily with local traffic peaks (for example, when users eat lunch in restaurants or take shelter from rain).
A major feature of reduce the cost of transmission is DAS solutions, operators can reduce the transmission cost by statistical multiplexing. Many users share the same transmission path and converge at the same site because in many places, dark fiber rental fees are relatively low. Since macro sites share macro RBS with dedicated indoor coverage sites, DRS solutions generally cost less than other solutions of the same kind. The investment cost of operators in the wireless access network is lower.