Cisco Aironet 2702i AIR-CAP2702I-E-K9 Merkblatt
Produktcode
AIR-CAP2702I-E-K9
© 2014 Cisco and/or its affiliates. All rights reserved. This document is Cisco Public Information.
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Nominal Configuration
Bandwidth
(MHz)
(MHz)
Number of
Spatial Streams
Spatial Streams
Constellation
Size and Rate
Size and Rate
Guard Interval
PHY Data Rate
(Mbps)
(Mbps)
Throughput
(Mbps)
(Mbps)
*
High-end product
80
3
256QAMr5/6
Short
1300
910
Amendment max
80
8
256QAMr5/6
Short
3470
2400
802.11ac 160 MHz
Low-end product
160
1
256QAMr5/6
Short
867
610
Mid-tier product
160
2
256QAMr5/6
Short
1730
1200
High-end product
160
3
256QAMr5/6
Short
2600
1800
Ultra-high-end product
160
4
256QAMr5/6
Short
3470
2400
Amendment max
160
8
256QAMr5/6
Short
6930
4900
*
Assuming a 70 percent efficient MAC, except for 802.11a, which lacks aggregation.
+
Assuming that 40 MHz is not available due to the presence of other APs.
2.3 How Do We Make 802.11ac Robust?
The sticker on the box that shows the
maximum data rate doesn’t help us much in the real world, where devices
have to contend with interference from non-802.11 devices, preexisting APs that might only use 20 or 40 MHz,
multipath fading, few antennas on mobile devices, weak signals at range, and so forth. What makes the raw speed
of 802.11ac so valuable are the extensions that help to deliver reliable throughput under realistic conditions.
2.3.1 Technology Overview
. This avoids much of the
interference at 2.4 GHz, including Bluetooth headsets and microwave ovens, and provides a strong incentive for
users to upgrade their mobile devices (and hotspot APs) to dual-band capability so that the 5-GHz band is more
universally usable. This choice also streamlines the IEEE process by avoiding the possibility of contention between
802.11 and
As we’ve already seen, 802.11 introduces higher-order modulation, up to 256QAM; additional channel bonding, up
to 80 or 160 MHz; and more spatial streams, up to eight. There is an alternative way to send a 160-MHz signal,
known as “80+80” MHz, discussed later (see
known as “80+80” MHz, discussed later (see
802.11ac continues some of the more valuable features of 802.11n, including the option of a short guard interval
(for a 10 percent bump in speed) and an incrementally better rate at range using the advanced low-density parity
check (LDPC) forward error-correcting codes. These LDPC codes are designed to be an evolutionary extension of
the 802.11n LDPC codes, so implementers can readily extend their current hardware designs.
Various space time block codes (STBCs) are allowed as options, but (1) this list is trimmed from the overrich set
defined by 802.11n, and (2) STBC is largely made redundant by beamforming. 802.11n defined the core STBC
modes of 2×1 and 4×2 and also 3×2 and 4×3 as extension modes, but the extension modes offered little gain for
their additional complexity and have not made it to products. Indeed, only the most basic mode, 2×1, has been
certified by the Wi-Fi Alliance. With this experience, 802.11ac defines only the core 2×1, 4×2, 6×3, and 8×4 STBC
modes, but again only 2×1 is expected to make it to products: if you had an AP with four antennas, why would you
be satisfied with 4×2 STBC when you could - and should - be using beamforming?
What 802.11ac also gets right is to define a single way of performing channel sounding for beamforming: so-called
explicit compressed feedback. Although optional, if an implementer wants to offer the benefits of standards-based
beamforming, there is no choice but to select that single mechanism, which can then be tested for interoperability.