Wireless : 802.11ac Wave 1 vs Wave 2 with single and multi user MIMO
Today I am going to talk about the difference between the Wave 1 and Wave 2 in wireless network 802.11ac. Wave 1 and Wave 2 are the basic terminology used in the wireless network on the Access points and we will cover the same in this article.
we will start with the 802.11ac Wave 1 first and then we will come up with the 802.11ac Wave 2. We will also come up with the difference between both of these at the end of this article.
802.11ac Wave 1
Wave 1 products use 20, 40 and 80 MHz channels in the 5 GHz channel space and is backward compatible with 11 n (and hence 11 a). The move to 5 GHz was necessitated by the much wider channels used by 11 ac – the good old 2.4 GHz band simply doesn't have the bandwidth to cope. 802.11ac uses 433 Mbps spatial streams (c.f. 11 n which uses 150 Mbps streams) and supports up to 3 spacial streams giving a maximum, theoretical PHY rate of c. 1.3 Gbps (maximum MAC throughput of approximately 845 Mbps).
Obviously, just like 11 n, with Wi-Fi being shared, speed and performance is directly related to the number of people sharing a network and the amount of available spectrum i.e. the amount of interference from neighboring Wi-Fi networks.
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| Fig 1.1- Single Vs Multi User MIMO |
Wave 1 Access Point's are similar to 11 n Access Point's which both support 3 spatial streams. This is done using a 3x3 SU-MIMO (single-user MIMO), that only allows an Access Point's base station to transmit to one client at a time on a channel.
802.11ac Wave 2
Wave 2 is a super-set of 802.11ac Wave 1. As such, it supports all the data rates of 802.11ac Wave 1. With the addition of support for 160-MHz-wide channels and the modulation and coding scheme (MCS) rates of 802.11ac, Wave 2 provides new maximum PHY rates based on the number of spatial streams and modulation
Wave 2 products, allow the use of 160 MHz wide channels or 80+80 bonded channels. Moving up to 160-MHz is good for bandwidth so, theoretically, this means more users can be supported with better performance. However, given that 160 MHz of relatively unused contiguous spectrum is impossible in the EU 5 GHz band, 11 ac products in the EU will continue to use 80 MHz frequency segments, enabling them to be placed more flexibly but will limit maximum performance.
However Wave 2 products can use up to 4 spacial streams (Wave 1 is only three) which allows a further performance gain.
One of the biggest upgrades in Wave 2 products is related to MU-MIMO. This is the multi-user version of MIMO technology that allows a base station to transmit to multiple users (up to 4) at a time giving several clients simultaneous access to a channel.
This means Access Point's can transmit to 4 single-stream devices such as 4 smart-phones at once.
The multi-user format is meant to boost user capacity. The MU-MIMO must be supported by both the Access Point and the client to be used since it relies on interoperable beam-forming. Some Wave 1 products that use SU-MIMO have integrated beam-forming to improve the performance.
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| Fig 1.2- Wave 1 Vs Wave 2 |
Wave 1 products have been in use in the market for about 2.5 years. Wave 2 builds upon Wave 1 with some very significant enhancements:
- Supports speeds to 2.34 Gbps (up from 1.3 Gbps) in the 5 GHz band
- Supports multi-user multiple input, multiple output (MU-MIMO)
- Offers the option of using 160-MHz-wide channels for greater performance
- Offers the option of using a fourth spatial stream for greater performance
- Can run in additional 5-GHz bands around the world
