Ipasolink Capacity - NEC IPASOLINK 400 Installation And Provisioning

Figure 8. Typical Ethernet frame. Preamble, Start of frame delimiter and Interframe gap (L1 overhead) are never
transmitted over the air. Optionally also MAC destination and Mac source adresses may be compressed.
The highlighted octets (20 octets) in Figure 8 are removed and instead three octets are added for internal
purposes. The net compression is 17 octets per frame. The effect of compression is only significant when
frames are very short (in the order of 64 to 512 octets). There is no compression gain at all when the
average frame size is large (e.g. 1500 octets/frame).
Optionally L2 layer compression of MAC addresses can be used. This will remove almost 12 octets,
assuming that only a very few MAC addresses are in use at a given time. In the same way as for L1
compression, removing some octets has no significance when the average frame size is large.
When talking about link capacity, it is always recommended to define if it is measured at the external
interface at L1 level (including and counting all octets) or if it is the L2 capacity. The difference is only
significant when small frames are used for the measurement.

IPASOLINK CAPACITY

Table 1 shows examples of maximum capacities available in iPasolink currently.
Modulation Channel
Spacing
(MHz)
256QAM 56
256QAM 56
256QAM 56
512QAM 56
512QAM 56
512QAM 56
Table 1. Example capacities at various frame sizes (L2 MAC compression not used)
The above figures show how the L1 capacity required at the external interface is much larger than the radio
capacity used for small frames. On the other hand, the available L2 radio capacity is best used with large
frames (internal use of three octets per frame becomes negligible).
For a reference, Table 2 shows the standard 1000 Mbit/s GbE L2 speeds for the same frame sizes as above.
As always, the available L2 speed depends on the frame size and the L1/L2 difference vanishes with large
frames.
Frame size Radio capacity L2
(L2 octets) + internal (Mbit/s)
64 367
1500 367
8000 367
64 412
1500 412
8000 412
External L1 L2 capacity
capacity transmitted
occupied (Mbit/s)
(Mbit/s)
460 350
371 366
367 367
517 394
417 412
413 412
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