Since the introducing of the CDMA technologies, processes of base station deployment have evolved to meet growing demands of mobile services. Regarding to the constraints related to co-locating 4G base station on existing 3G and 2G sites, Distributed Cell Architecture has become a cost-effective way for Operators to get the expected performance with lower investments.
Distributed Cell System is designed to overcome the problems related to that it has become difficult to share the existing sites with the 4G base station without decreasing the whole system performance, which would be damaging and would go against the desired objective sought by deploying the 4G technologies like LTE and Advanced-LTE.
DCS is based on the use of a RF repeater or RF head placed in a remote location and connected on one side to the remote antennas placed in a suitable configuration regarding to coverage and traffic criterias, and connected on the other side to the BTS by mean of a fiber-optic link or by mean of a wireless or optical link.
In order to achieve a sufficient input to output isolation, a high immunity against spurious and broadband inreferences and a low signal distorsion needed to preserve the signal strength and quality, one can use an optical repeater which can be placed close to the antennas to avoid feeder losses and thus saving the BTS output power.
This deployment architecture provides an apropriate way for 4G sites to get the coverage and the traffic flow desired without the restriction of co-locate the antennas with the BTS in existing sites. It is suitable for both outdoor and in-building coverage purpose.
However using an analog signal processing throughout analog devices requires a fine tuning and a specific design to achieve the required performance levels. Since a repeater would be in use by various Service Providers and thus would operate in different sub-bands within the same frequency range, the use of digital filtering looks to have a better performances regarding to the curve sharpness for outband attenuation and at the same time has the ability to be easily programmable by the software related to a DSP circuit. This feature is greatly appreciated to save time when tuning the filters in the desired sub-band.
On the other hand, the use of a WDM optical transceiver with a DFB laser operating in the wavelength range 1100 to 1500 nm in conjuction with digital filters gives a lower noise level and suprious and as well a lower signal distorsion. The immunity of the equipment is greatly profitable to connect more than one Remote Unit to the Master Unit in a daisy chain configuration.
Considering the channelized digital repeater for narrow band application (e.g. TETRA), since broadband amplifiers are often used for both uplink and downlink signals in the wireless subsystem, filters can be easily re-tuned to reject the adjacent channels in multiple spectrum bands. Such a transceiver would be particularly useful to avoid interferences especially when two co-located users operate in the same frequency range.
MCR TELECOMMUNICATION provides MAOR90822LH32
repeater with advanced digitalized WDM transceiver built-in allowing each channel to connect 4 Remote Units in daisy-chain configuration over a one duplex single mode fiber. One Master Unit handles up to 8 channels. This feature is highly suitable for large building and tunnel coverage where the use of RF repeater is not recommended. For more details refer to the MAOR seies datasheet.