1 Introduction
2 Related works
2.1 QoS-aware strategies for real-time traffic
2.2 QoS-aware strategies for heterogeneous traffic
2.3 QoS-aware strategies for bit rate guarantees
3 System model
k,K
| Bearer index and set of all bearers in cell |
s,S
| Resource block index and number of available resource blocks |
m,M
| QCI index and set of all QCIs |
T
| Transmission Time Interval |
P
k
[n,s] | Priority of bearer k on resource block s and TTI n
|
R
k
[n,s] | Achievable transmission rate of bearer k on resource block s
|
and TTI n
| |
R
MCS
| Rate of selected MCS |
\(\overline {r_{k}[n]}\)
| Low pass filtered data rate that bearer k has received |
until TTI n
| |
α
| Degree of fairness factor |
w
k
[n] | Head of Line delay of bearer k measured in TTI n
|
q
k
[n] | Number of bits in queue of bearer k measured in TTI n
|
f(w
k
) | Delay-dependent factor in priority computation |
D
| Target packet delay of delay-dependent factor |
a
k
| Slope adjustment factor for sigmoid function |
r
lb
| Lower bound for \(\overline {r_{k}[n]}\)
|
\(F_{k}^{\text {QCI}_{m}}\)
| QCI relative prioritization factor for bearer k mapped |
onto QCI
m
| |
Q
k
| Quality performance indicator for bearer k, (see (9)) |
q
k
[n] | Queue length of bearer k in TTI n
|
λ
k
| Estimator of the average arrival bit rate on bearer k
|
r
k
[n] | Transmitted data rate in TTI n by bearer k
|
Quality performance indicator of the bearer with | |
\(Q^{\text {QCI}_{m}}\)
| worst quality among all bearers mapped onto QCI
m
|
that have sufficient radio channel quality | |
\(\text {TQ}^{\text {QCI}_{m}}\)
| Minimum quality level for bearer k mapped on |
to QCI
m
| |
F
| Priority enhancing factor |
4 QoS concept in 3GPP
4.1 The EPS bearer concept
-
QoS Class Identifier (QCI): is a reference scalar used to specify node-specific parameters that control bearer-level packet forwarding treatment.
-
Guaranteed Bit Rate (GBR): is the bit rate the GBR bearer is expected to provide.
-
Maximum Bit Rate (MBR): is the maximum bit rate a GBR bearer can provide (e.g., a traffic shaper may discard the traffic excess). In Release 8, the MBR of a GBR bearer shall be set equal to the GBR [1].
4.2 Standardized QCI characteristics
-
Resource type (GBR or non-GBR): determines if the bearers associated to a given QCI are GBR or not.
-
Priority: via its QCI, a bearer is associated with a priority level, which can be used to prioritize between bearers. Note that a QCI with lower priority parameter has preference over a QCI with higher priority parameter.
-
Packet Delay Budget (PDB): it defines the upper limit of the delay suffered by a packet between the UE and the Policy and Charging Enforcement Function (PCEF).
QCI | Resource | Packet | Packet | ||
---|---|---|---|---|---|
type | Priority | Delay | error | Example services | |
Budget (ms) | loss rate | ||||
1 | GBR | 2 | 100 | 10−2
| Conversational voice |
2 | 4 | 150 | 10−3
| Conversational video (live streaming) | |
3 | 3 | 50 | 10−3
| Real-time gaming | |
4 | 5 | 300 | 10−6
| Non-conversational video (buffered streaming) | |
5 | Non-GBR | 1 | 100 | 10−6
| IMS signalling |
Video (buffered streaming), TCP-based (e.g., | |||||
6 | 6 | 300 | 10−6
| www, e-mail, chat, ftp, p2p file sharing, | |
and progressive video) | |||||
7 | 7 | 100 | 10−3
| Voice, video (live streaming), interactive | |
gaming | |||||
8 | 8 | 300 | 10−6
| Video (buffered streaming), TCP-based (e.g., | |
www, e-mail, chat, ftp, p2p file sharing, | |||||
9 | 9 | and progressive video) |
4.3 Implications of the bearer QoS profile on the scheduling framework
5 QoS scheduling framework
5.1 Scheduling for non-GBR bearers
5.2 Scheduling for GBR bearers
5.3 QCI prioritization
-
For GBR QCIs: \(\text {TQ}^{\text {QCI}_{m}}\) is a delay threshold for QCI m .
-
For non-GBR QCIs: \(\text {TQ}^{\text {QCI}_{m}}\) is a data rate threshold for QCI m .
6 Performance results
6.1 Simulation setup and parameters
Parameter | Setting | |
---|---|---|
Carrier frequency | 2 GHz | |
System bandwidth | 10 MHz | |
Inter-site distance | 2 km | |
Std of shadow fading | 8 dB | |
Power delay profile | ITU typical urban 20 paths | |
Antenna scheme | SIMO 1×2 – rx (MRC) | |
UE speed for fast fading process | 3 km/h | |
Total eNode-B transmit power | 46 dBm | |
Pilot, control channel overhead | 3/7 symbols | |
QPSK: 1/3, 1/2, 2/3 | ||
Modulation/coding rate settings | 16QAM: 1/2,2/3, 4/5 | |
64QAM: 2/3, 4/5 | ||
CQI estimation | Ideal (std of estimation error 0 dB) | |
HARQ model | Ideal chase combining | |
a
k
= 75, c = 4, 3D/2 = PDB | ||
Scheduling parameters |
r
lb
= 100 kbps, ρ
d
= 1/100 | |
ρ
r
= 1/300, F = 4 dB | ||
Insufficient radio channel quality | G Factor ≤−3 dB | |
Services | QCI2: live video streaming |
\(\text {TQ}^{\text {QCI}_{2}}\) = 125 ms, PDB = 150 ms |
QCI4: buffered video streaming |
\(\text {TQ}^{\text {QCI}_{4}}\) = 250 ms, PDB = 300 ms | |
QCI8: web |
\(\text {TQ}^{\text {QCI}_{8}}\) = 600 kbps | |
QCI9: ftp |
\(\text {TQ}^{\text {QCI}_{9}}\) = 600 kbps | |
Traffic Mix Cases | Equal Load | 25 % load per service |
Heavy Load live video streaming | 40 % live video | |
20 % other services | ||
Heavy Load buffered video streaming | 40 % buffered video | |
20 % other services | ||
Heavy Load web | 40 % web, 20 % other services | |
Heavy Load ftp | 40 % ftp, 20 % other services |
6.2 Simulation results
6.2.1 Sensitivity to prioritization factor F
6.2.2 Evaluation with different traffic mixes
QCI2
| QCI4
| QCI8
| QCI9
| |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Cell throughput | UEs that do not | Avg. UE | UEs that do not | Avg. UE | UEs with | Avg. UE | UE throughput at | UEs with | Avg. UE | UE throughput at | ||
(Mbps) | fulfill PDB (%) | throughput | fulfill PDB (%) | throughput | throughput | throughput | 95th percentile | throughput | throughput | 95th percentile | ||
(kbps) | < 512 kbps (%) | (Mbps) | (Mbps) | < 512 kbps (%) | (Mbps) | (Mbps) | ||||||
Equal | PF | 11.48 | 0.85 | 240 | 4.79 | 437 | 2.09 | 3.18 | 10.59 | 2.89 | 2.63 | 7.81 |
Load | QoS | 11.48 | 0 | 239 | 0 | 434 | 0.25 | 4.04 | 16.02 | 4.92 | 3.12 | 10.26 |
Exp | 11.48 | 0 | 241 | 0 | 437 | 4.67 | 2.97 | 10.20 | 4.49 | 2.47 | 7.56 | |
H. L. | PF | 11.60 | 0.08 | 240 | 5.16 | 439 | 1.99 | 3.01 | 9.58 | 2.20 | 2.47 | 5.86 |
live | QoS | 11.60 | 0 | 240 | 0 | 436 | 0.40 | 3.91 | 14.63 | 4.4 | 3.00 | 9.09 |
video | Exp | 11.60 | 0 | 240 | 0 | 439 | 6.16 | 2.71 | 8.88 | 6.05 | 2.25 | 5.60 |
H. L. | PF | 11.77 | 0 | 240 | 7.14 | 438 | 3.74 | 2.92 | 9.80 | 4.11 | 2.12 | 5.80 |
buff. | QoS | 11.77 | 0.48 | 239 | 0.58 | 435 | 3.34 | 3.60 | 14.83 | 11.98 | 2.40 | 7.74 |
video | Exp | 11.77 | 0 | 240 | 0 | 439 | 10.44 | 2.61 | 9.31 | 12.70 | 1.91 | 5.23 |
H. L. | PF | 11.27 | 0 | 240 | 4.57 | 439 | 1.66 | 3.57 | 11.70 | 1.65 | 2.97 | 8.14 |
web | QoS | 11.27 | 0 | 239 | 0 | 439 | 0.67 | 4.56 | 17.41 | 5.69 | 3.56 | 11.45 |
Exp | 11.27 | 0 | 240 | 0 | 440 | 3.75 | 3.41 | 11.36 | 3.49 | 2.85 | 8.15 | |
H. L. | PF | 11.67 | 0.49 | 240 | 6.09 | 438 | 2.61 | 3.30 | 10.86 | 3.04 | 2.78 | 8.34 |
ftp | QoS | 11.67 | 0 | 239 | 0 | 434 | 0 | 4.09 | 16.14 | 6.44 | 3.20 | 10.9 |
Exp | 11.67 | 0 | 240 | 0 | 438 | 5.54 | 3.10 | 10.32 | 6.18 | 2.66 | 7.80 |