Rack sharing: In addition to the extended site–sharing option, operators can choose to install their active equipment in a shared cabinet or rack (i.e., the housing frame encompassing the electronic and other hardware). In this rack-sharing option, other elements such as channel elements, transmitter and receiver (TRXs) and power amplifiers remain physically separated, along with the transmission networks and other elements of radio access, such as the Radio Network Controllers (RNCs). Power supply, air-conditioning, ancillary cabinet and alarm installations can be shared.[1]
Depending on the actual situation, rack sharing may provide up to 5 per cent capital expenditure savings for an operator, per Node-B. If battery backup is shared, this option may provide even further savings. Figure 1 graphically illustrates this option.
Figure 1: Rack Sharing
(i.e., sharing the physical frame housing electronics and other equipment and ancillary elements such as power supply, air-conditioning, battery back-up, and alarm installation)
Source: Camila Borba Lefèvre, Mobile Network Sharing, at: www.itu.int/ITU-D/treg/Events/Seminars/GSR/GSR08/papers.html
Full Radio Access Network (RAN) Sharing: In addition to extended site-sharing and rack sharing, operators may also share all the elements of the Node-B. In case independent frequency control needs to be in place, the TRX and the power amplifier (PA) should remain independent, allowing for radiation at each operator’s assigned frequency range. When the spectrum can be shared, operators may also share the TRX and the PA.
Figure 2: Full RAN Sharing
Source: Camila Borba Lefèvre, Mobile Network Sharing, at: www.itu.int/ITU-D/treg/Events/Seminars/GSR/GSR08/papers.html
In the case of full RAN sharing, regulatory authorities may require the shared elements to be functionally separated. In this scenario, operators should retain independent control of all the parameters that determine the quality of the network, such as coverage, speed and the handover parameters. The Dutch regulatory authority required functional separation when it assessed the proposed sharing arrangement for 3G mobile services between operators Ben and Dutchtone.[2]
Functional separation implies that the communication between the RNC and the Node-B has to be under the independent control of one operator, as far as that operator’s service is concerned. This communication may take place using the same cables and connections, but it must be logically separated. In addition, operations, maintenance and network control should be separated. Those elements may be under individual control by each operator or under joint control of an independent third party, which would operate the shared network on behalf of the sharing parties. This independent third party could be a joint venture between the sharing parties or an independent company. Figure3 illustrates a functionally separated RNC, which may be necessary due to regulatory requirements.
Figure 3: Separating the RNC Functions
Source: Camila Borba Lefèvre, Mobile Network Sharing, at: www.itu.int/ITU-D/treg/Events/Seminars/GSR/GSR08/papers.html
[1] This situation may also be called “ancillary sharing”.
[2] See Decision of NMa of 11 October 2002, Case No. 2816/35.