WiMAX Standard 802.16 mentions following 5 QoS classes: • Unsolicited Grant Service(UGS) • Extended Real Time Polling Service(ertPS) • Real Time Polling Service(rtPS) • Non Real Time Polling Service(nrtPS) • Best Effort Service(BE) Each of these wimax QoS classes has their own parameters such as bandwidth request type, min. throughput requirement as well as delay or jitter constraints.

1. WiMAX QoS Classes-UGS, rtPS, ertPS, nrtPS, BE QoS types
WiMAX Standard 802.16 mentions following 5 QoS classes:
• Unsolicited Grant Service(UGS)
• Extended Real Time Polling Service(ertPS)
• Real Time Polling Service(rtPS)
• Non Real Time Polling Service(nrtPS)
• Best Effort Service(BE)
Each of these wimax QoS classes has their own parameters such as bandwidth request type, min. throughput requirement as well as
delay or jitter constraints.
UGS
This Wimax QoS class provides fixed bandwidth allocation on periodic basis. Once the connectivity is established, no more requests are
needed. For application of this type refer table-1. QoS parameters for this type are MST, tolerated jitter and max. latency. Refer-table 2
for comparison with other wimax QoS types.
ertPS
This QoS type is developed to support VOIP along with silence suppression. There will be no traffic transmission during silence time.
QoS parameters are same as UGS type. Check table-1 for application of this type. ertPS is similar to UGS in which base station assigns
MST on active mode and no BW is allocated during silent time period. Here BS need to poll mobile subscriber to know whether silent
period has been ended or it is continuing.
rtPS
It is used for VBR real time traffic for example MPEG video. Unlike UGS where in fixed allocation is made by BS, here BS regularly polls
MS to findout allocation need. Hence bandwidth is allocated on need basis and is adaptive in nature. For this wimax QoS type Min.
reserved traffic rate and MST need to be mentioned separately. For UGS and ertPS Min. reserved traffic rate and MST are both same.
QoS parameters are same as UGS.
nrtPS
This type is used for non real time Variable bit rate traffic with no delay guarantee. But min. rate is guaranteed. FTP falls under this QoS
type.
BE
In this class, BW is granted to mobile subscriber if and only there will be left over bandwidth from other QoS classes. This QoS class
guarantees neither delay nor throughput. It allows min. reserved traffic rate and max. Sustained traffic rate.

2. WiMAX
QoS
type Applications/Uses Scheduling
Bandwidth requests/
BW REQ types
Parameters/
specifications
UGS
CBR real time
traffic(periodic), for
example T1/E1 connection
Static allocation type,
grant equal to
MST(Maximum
Sustained Traffic Rate)
Reserves bandwidth during setup time, poll-me bit
for unicast polling, no piggyback requests, no
bandwidth strealing.
No other kinds of polling, GM can be used for BW
REQ in case of rate mismatch compensation
MST equal to Min. reserved traffic rate, max. latency,
tolerated jitter, uplink grant scheduling type,
unsolicited grant interval
ertPS
VOIP(silence suppression),
video conference(real
time variable size
data,periodic) Dynamic allocation
reserves bandwidth during setup, allows piggyback
requests, allows bandwidth stealing. allows all kinds
of poling
MST is equal to min. reserved traffic rate, max. latency
and unsolicited grant interval
rtPS
Real time video(real time
variable size data on
periodic basis) Dynamic allocation
allows piggyback,bandwidth stealing and unicast
polling
Min.reserved traffic rate, max. sustained traffic rate,
max. latency and uplink grant scheduling type
nrtPS FTP, variable size data Dynamic allocation
allows piggyback,bandwidth stealing and all kinds of
polling
Min. reserved traffic rate, max. sustained traffic rate,
traffic priority and uplink grant scheduling type
BE Web Traffic Dynamic Allocation
Allows piggyback, bandwidth stealing and all kinds
of polling
Min. reserved traffic rate, Max. sustained traffic rate,
traffic priority and uplink grant scheduling type
Table-1
Let us compare to check similarities and difference between various WIMAX QoS classes.
WiMAX QoS PROS CONS
UGS
No overhead, meet guaranteed latency of Mobile Subscriber requests
for real time service Bandwidth may not be utilized fully as they are granted irrespective of need
ertPS Optimal latency and data overhead efficiency Need to use polling and mechanism to inform BS when the traffic starts during silence.
rtPS Optimal data transport efficiency requires overhead of BW REQ and polling latency
nrtPS
provides efficient service for non real time traffic with min. reserved
rate Not Applicable
BE Provides efficient service for BE(Best Effort) Traffic No service guarantee, some connections may stay for long time period
Table-2