Chapter 1: Product description
Wireless operation
Page
1-16
TDD frame parameters
The TDD burst duration varies depending on the following:
•
Channel Bandwidth
•
Cyclic Prefix
•
Frame Period
•
Frame configuration - Downlink Data
•
Link operation – Dynamic Rate Adaptation
OFDM and Channel Bandwidth
The PMP/PTP 450 Platform Family transmits using Orthogonal Frequency Division Multiplexing (OFDM).
This wideband signal consists of many equally spaced sub-carriers. Although each sub carrier is
modulated at a low rate using conventional modulation schemes, the resultant data rate from the sub-
carriers is high. OFDM works exceptionally over a Non-Line-of-Sight (NLoS) channel.
The channel bandwidth of the OFDM signal is configurable to one of the following values: 5, 7, 10, 15, 20,
30, and 40 MHz. Higher bandwidths provide greater link capacity at the expense of using more
bandwidth. Systems configured for a narrower channel bandwidth provide better receiver sensitivity
and can also be an appropriate choice in deployments where the amount of free spectrum is limited.
Note
The channel bandwidth must be configured to the same value at both ends of the link. Not
all channel bandwidths are available in all regulatory bands.
Cyclic Prefix
OFDM technology uses a cyclic prefix, where a portion of the end of a symbol (slot) is repeated at the
beginning of the symbol (slot) to allow multi-pathing to settle before receiving the desired data. A 1/16
cyclic prefix means that for every 16 bits of throughput data transmitted, an additional bit is used. For
your convenience, the 450 Platform Family ODUs have been locked to a 1/16 CP.
Frame Period
The frame period or frame duration is the time between the beginning of a frame and the end of the
frame. The 450 Platform Family supports two frame periods: 2.5 ms and 5 ms.
The 5ms frame period configuration provides higher throughput as a result of reduced frame overhead
during transmission. In turn, the 2.5 ms frame period configuration affords reduced latency in the
system, half of that introduced by the 5 ms frame configuration.
Содержание PMP 450 AP
Страница 79: ...Chapter 2 System hardware System Components Page 2 29 Figure 20 Gigabit Enet Capable power supply...
Страница 160: ...Chapter 3 System planning Radio Frequency planning Page 3 30 Figure 55 Sector Antenna...
Страница 161: ...Chapter 3 System planning Radio Frequency planning Page 3 31 Figure 56 cnMedusa Antenna...
Страница 189: ...Chapter 3 System planning Remote AP Deployment Page 3 59 Figure 65 Remote AP wired to SM that serves as a relay...