Design Considerations; Wireless Mesh Constraints; Wireless Backhaul Data Rate - Cisco Mesh Access Points Deployment Manual

Design Considerations

This chapter describes important design considerations and provides an example of a wireless mesh design.
Each outdoor wireless mesh deployment is unique, and each environment has its own challenges with
available locations, obstructions, and available network infrastructure. Design requirements driven by expected
users, traffic, and availability needs are also major design criteria. This chapter contains the following sections:
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Wireless Mesh Constraints

The following are a few system characteristics to consider when you design and build a wireless mesh network.
Some of these characteristics apply to the backhaul network design and others to the CAPWAP controller
design:

Wireless Backhaul Data Rate

Backhaul is used to create only the wireless connection between the access points. The backhaul interface by
default is 802.11a or 802.11a/n depending upon the access point. The rate selection is important for effective
use of the available RF spectrum. The rate can also affect the throughput of client devices, and throughput is
an important metric used by industry publications to evaluate vendor devices.
Dynamic Rate Adaptation (DRA) introduces a process to estimate optimal transmission rate for packet
transmissions. It is important to select rates correctly. If the rate is too high, packet transmissions fail resulting
in communication failure. If the rate is too low, the available channel bandwidth is not used, resulting in
inferior products, and the potential for catastrophic network congestion and collapse.
Data rates also affect the RF coverage and network performance. Lower data rates, for example 6 Mbps, can
extend farther from the access point than can higher data rates, for example 300 Mbps. As a result, the data
rate affects cell coverage and consequently the number of access points required. Different data rates are
achieved by sending a more redundant signal on the wireless link, allowing data to be easily recovered from
noise. The number of symbols sent out for a packet at the 1-Mbps data rate is higher than the number of
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Wireless Mesh Constraints, page 51
ClientLink Technology, page 55
Controller Planning, page 58
C H A P T E R
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