Product Info

System Description WipLL Radio Technology - Physical Layer
25030311-08 Airspan Networks Inc. 2-33
2.6.5.4. Calculation Example
This example assumes that the required services are based on voice traffic of 100
merlangs per subscriber and a CIR of 256 Kbps. In addition, in this example, a 1%
blocking is expected for voice calls, and 1:10 over subscription is expected for data.
The number of subscribers that can be supported by a single BSR (N) is equal to
Kbps
KbpsN
CodecCallsSim
Kbps
GostrafficCalls 000,4
%80
256%10
)(_
000,4
),( ≤
⋅
⋅
+⋅
Assume that N = 40. Therefore, the aggregate voice traffic is equal to 4 erlangs.
Using Erlang B tables with 1% blocking, 10 voice channels (calls) are required. For
G.729 with 40 msec sample interval and silence suppression, the total capacity set
for voice is obtained by 10*143 Kbps*65% = 930 Kbps. The total capacity set for
data is obtained by 40*256 Kbps*10%/80% = 1,280 Kbps. This implies that more
subscribers can be supported, since the aggregated capacity (2,210 Kbps) is lower
than the 4 Mbps limit. If N (BSRs) increases, the limit of 4 Mbps will be reached for
N = 80. (The process of finding N can be simplified by using an electronic
spreadsheet).
2.6.6. Selecting an Appropriate Operation Mode
WipLL enables the operator the flexibility to choose between several modes of
operation according to the operator’s needs. One of the optional modes relates to the
symbol rate of the modem. This section presents the main issues that should be
considered when selecting an operation mode when deploying the WipLL system.
2.6.6.1. WipLL Multiple Modes
WipLL offers the capability to select between two operating modes in terms of
symbol rate. The modem can operate in either 1 Mega symbols per second (Msps) or
1.33 Msps. The operating mode is software selectable for each BSR. The differences
between the modes of operation are related to the bit rate and the channel bandwidth.