Because there has been no QoS standard for WiFi, VoIP providers like SpectraLink have made their own prioritization protocols available to other vendors. SpectraLink’s QOS protocols are also used by Chantry Networks, Cisco Systems and Meru Networks.
The IEEE expects to finalize its 802.11e QoS standard in spring 2005. The 802.16 standard may have an advantage in that area, with a QOS system ready to go.
Wireless Net Design explains How 802.16 Tackles Quality of Service in a three-part article:
The IEEE 802.16 specification is breaking the QoS “gridlock” that has traditionally plagued broadband wireless equipment designs. The issue of QoS, therefore, has become a critical area of concern for suppliers of broadband wireless access (BWA) equipment and their customers.
Enforceable QoS is an essential foundation for widespread acceptance of broadband wireless, since it allows for more efficient sharing of the operator’s infrastructure as demand for capacity increases with subscriber take-up.
What 802.16 brings to the QoS equation is a number of unique QoS parameter sets that guarantee levels for throughput, latency, and jitter.
By way of definition, QoS metrics measure loss, throughput, delay and delay variation (also known as jitter), sequencing, and total errors. These metrics are equally applicable at the data link layer and the network layer, and have been generally adopted by industry groups for testing QoS over networks such as ATM, Frame Relay and IP.
Much of ATM’s success is directly attributable to its QoS guarantees. ATM’s attempt to deliver QoS is defined by different classes of service based on constant and variable bit rates. These classes are:
- Constant bit rate (CBR) In CBR, traffic is characterized by a continuous stream of bits at a steady rate. This class is for low-bandwidth traffic that is highly sensitive to delay and intolerant to cell loss.
- Variable bit rate (VBR) VBR applies to voice or video applications that use compression. Within this class are real-time VBR (RT-VBR) where real-time end-to-end delivery is critical and non-real time VBR (VBR-NRT), where delay is less critical.
- Best effort services These include available bit rate (ABR) and unspecified bit rate (UBR) and apply to LAN traffic that is more tolerant of delays and cell loss. Since UBR is subject to increased cell and packet loss and does not specify bit rate or traffic parameters, it has no QoS guarantees.
What specifically sets the 802.16 standard apart is a polling-based MAC layer that is more deterministic than the contention-based MAC used by 802.11.
Each connection is associated with a single scheduling data service and each data service is associated with a set of QoS parameters that quantify aspects of its behavior. The following are the four types of scheduling service supported by 802.16:
- Unsolicited Grant Service (UGS)
- Real-time Polling Service (rtPS)
- Non-real-time Polling Service (nrtPS)
- Best Effort (BE)
The article’s three parts (part one, part two and part three) go into considerable detail.
