IEEE 802.11ad Defining the Next Generation Multi-Gbps WiFi

IEEE 802.11ad Defining the Next Generation Multi-Gbps WiFi

Group AD (TGad) began the process of developing a 60 GHz amendment to 802.11.


The VHT SG began in May 2007. Initial presentations highlighted the benefits of advanced technology in microwave bands. However, to address single link data rates in the giga-bit per second range, the group began investigating opportunities in the 60 GHz ISM band [7]. This led to the development of a 60 GHz PAR [8].

The 60 GHz PAR outlined the scope of PHY and MAC modifications to the 802.11 standard. The primary requirement is that the amendment must enable a throughput of at least 1 Gbps at the top of the MAC. The use of the term throughput dictates that MAC efficiency must be addressed, not just an improvement to the PHY data rate.

As described in Section I, several other organizations are also defining specifications for 60 GHz operation, particularly IEEE 802.15.3c. Two requirements in the PAR address distinct identity from other groups. The first is maintaining the 802.11 user experience. This means maintaining the network architecture of the 802.11 system, e.g. infrastructure basic service set, extended service set, access point, station. This also implies reusing and maintaining backward compatibility to the 802.11 management plane, e.g. association, authentication, security, measurement, capability exchange, management information base (MIB). The other requirement addressing distinct identity is fast session transfer between PHY’s. A fast session transfer mechanism could provide seamless rate fall back between VHT and 802.11n for multi-band devices. Consumers will be provided their expected WLAN coverage from combo 60 GHz and 2.4 / 5 GHz devices.

A great deal of discussion took place in VHT SG regarding coexistence with various other systems in the 60 GHz band. As such, the 60 GHz PAR has a requirement that the system will provide mechanisms that enable coexistence with other systems.

In a parallel effort in VHT SG, usage models were discussed in order to set the framework for the type of applications that may be targeted by this next generation technology. The Wi-Fi Alliance presented a collection of usage models requiring higher throughput than available by current technology [10]. These included wireless display, in home distribution of HDTV and other content, rapid upload and download of large files to/from a server, backhaul traffic, campus / auditorium deployments, and manufacturing floor automation. The WFA report did not specify which band of operation would be better suited to which usage model. There was some discussion in the study group to identify which of the WFA usage models would be more suited to <6 GHz versus 60 GHz [11]. Short distance, single link applications requiring high data rates like uncompressed video and desktop storage and display were associated solely with 60 GHz. However, other applications like lightly compressed video streaming around a home were mapped to <6 GHz.


TGad began in January 2009. The initial plans were highlighted to be the development of the following task group documents: selection procedure, functional requirements, evaluation methodology, and channel models. An initial proposal for a selection procedure in [12] describes a “call for complete proposals” procedure. A proposal is considered complete if it addresses all the functional requirements and evaluation methodology requirements. In [12], the expectation is that the task group documents will be complete by January 2010 and presentation of complete proposals will occur in May 2010.

A. Functional Requirements

The approved initial draft of the TGad Function Requirement document is [13]. Most of the requirements mirror those in the PAR; however there are three additional requirements. First, all devices are required to support a maximum PHY rate of at least 1 Gbps. Second, the amendment must provide a means of achieving 1 Gbps throughput at a range of at least 10m in some NLOS conditions. This mostly means that transmit beamforming scheme will be included as part of TGad. The third additional requirement is actually a set of requirements to support uncompressed video. The ability to support uncompressed video is a major differentiating feature from 2.4 / 5 GHz 802.11 systems. A rate of 3 Gbps throughput with a packet loss rate of 1e-8 and a maximum delay of 10 msec must be supported. The basis of these requirements is uncompressed 1080p video. B. Evaluation Methodology

The TGad Evaluation Methodology document defines conditions for functional requirements compliance (with a simple synthetic point-to-point test case), PHY performance (PER vs. SNR curves using a 60 GHz channel and hardware impairments), and a limited set of simulation scenarios and comparison criteria for evaluating proposals [14]. While much work has gone into developing [14], the task group has yet to approve an initial draft.

For 802.11n, the task group defined a large set of simulation scenarios, of which only a very small number were ever used to compare proposals. Learning from this, the current version of the TGad Evaluation Methodology document only defines three simulation scenarios addressing the most likely markets. These scenarios are home living room, office conference room, and enterprise cubicle. In the home living room, the usage scenario is a set top box transmitting uncompressed video to the TV.

The office conference room consists of six laptops, a projector, a hand held device, and an access point. This scenario includes a range of applications. First, a laptop is transmitting lightly compressed video to the projector. Second, multiple laptops are performing local file transfer from the AP or between the laptops. Third, multiple laptops are performing web browsing via the AP. The last application includes a laptop engaged in sync-and-go with the handheld device.

The enterprise cubicle scenario defines a cubicle layout with each cubicle containing a laptop simultaneously transmitting lightly compressed video to a monitor, connected to an AP, and wirelessly connected to a hard drive. Multiple cubicles will be simulated to model interference between cubicles, especially when there are not enough free channels to avoid overlap.

In order to simulate these scenarios, traffic models are required. Uncompressed video is assumed to be 3 Gbps

This full text paper was peer reviewed at the direction of IEEE Communications Society subject matter experts for publication in the IEEE CCNC 2010 proceedings

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