International Journal of Scientific & Engineering Research, Volume 5, Issue 7, July-2014 1193

ISSN 2229-5518

Performance Analysis of Channel Models of

LTE in Various Transmission Modes

Rashedul Haque Chowdhury1, Mostarina Zinnat-Ara2, Dilara Afroz3

Abstract— Long Term Evaluation (LTE) is an emerging 4G wireless technology.Multiple-Input Multiple-Output (MIMO) systems are a primary enabler of the high data rate to be achieved by LTE . According to LTE Release 9 there are 7 MIMO configurations from mode 2 to 8. An LTE base station is expected to select and switch among these transmission modes based on channel quality feedback like Channel Quality Indicator (CQI). And the ITU standard multipath channel models proposed by ITU used for the development of 3G

'IMT‐2000' group of radio access systems are basically similar in structure to the 3GPP multipath channel models. In this paper we have investigated the effect of different multipath channel models at different SNR levels on the performance achieved through transmission mode 1 to 4. The simulation output shows that the mode 3 and 4 which are open loop and close loop spatial multiplexing respectively using

4 transmitting antenna outperforms all other mode in terms of high throughput at very reasonable BLER.

Index Terms— LTE, Transmission Modes, PedA, PedB, AW GN, CQI, Throughput

—————————— ——————————


In This Paper we have investigated the effect of ITU Multi- path Channel Model proposed by ITU [1] on the performance of LTE Release 9 through LTE link level simulator developed by the Institute of Communications and Radio Frequency En- gineering, Vienna University of Technology[2]. The aim of these channel models is to develop standards that help system designers and network planners for system designs and per- formance verification.
This paper is made for the developing countries, who are migrating towards 4G LTE Technology, so that they can use this as a helping manual. That's why transmission mode 1-4 are simulated in high multipath fading environment and the superiority of the open loop and close loop spatial multiplex- ing were demonstrated.
The paper is organized in following section. In section two we have presented the over view of LTE transmission modes
& CQI Feedback and Multipath Channel Model in Section three. In Release 8, Long Term Evaluation(LTE) [3] was stand- ardized by 3GPP as the successor of the Universal Mobile Tel- ecommunication System (UMTS). The targets for downlink and uplink peak data data rate requirements were set to
100Mbits/sec and 50Mbits/sec, respectively when operating in a 20MHz spectrum allocation [4].
First performance evaluations show that the throughput of the LTE physical layer and MIMO enhanced WCDMA [4] is approximately the same [6-10] . However, LTE has several other benefits of which the most important are explained in the fol- lowing.
thogonal Frequency Division Multiple Access (OFDMA) which converts the wide-band frequency selective channel into a set of many flat fading sub-channels. The flat fading sub-channels have the advantage that even in the case of MIMO transmission – optimum receivers can be implemented with reasonable complexity, in contrast to WCDMA systems . OFDMA additionally allows for frequency domain schedul- ing, typically trying to assign only "good" sub-channels to the individual users . This offers large throughput gains in the downlink due to multi-user diversity [11, 12].


2.1 Transmission Mode Downlink

In the downlink, LTE uses technologies such as MIMO, trans- mit diversity or SISO, Beamforming etc are used to achieve high data rates. In the Release 9 specification [13], up to four antennas are defined in the base station and up to four anten- nas in the UE [14].


1currently pursuing Masters Degree Program in Telecommunication En- gineering in East West University, Bangladesh. E-mail:

2, 3 completed Bachelor Degree program in Electrical & Electronic Engi-

neering in Ahsanullah University of Science & Technology, Bangladesh. E-mail: 2 , 3

The LTE downlink transmission scheme is based on Or-

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Here we discussed about Transmission Mode 1,2,3,4. Transmission Mode 1 is Single transmit antenna [14].
Transmission Mode 2 is Transmit diversity which sends the same information via various antennas, whereby each antenna stream uses different coding and different frequency re- sources. This improves the signal-to-noise ratio and makes transmission more robust. For two antennas, a frequency- based version of the Alamouti codes (space frequency block code, SFBC) is used, while for four antennas, a combination of SFBC and frequency switched transmit diversity (FSTD) is used [14] .
Transmission Mode 3 is Open loop spatial multiplexing with CDD which supports spatial multiplexing of two to four layers that are multiplexed to two to four antennas, respective- ly, in order to achieve higher data rates. It requires less UE feedback regarding the channel situation (no precoding matrix indicator is included), and is used when channel information is missing or when the channel rapidly changes, e.g. for UEs moving with high velocity [14].

Fig 1: Transmission Mode (TM) 3, Spatial multiplexing with
Transmission Mode 4 is closed loop spatial multiplexing with up to four layers that are multiplexed to up to four an- tennas, respectively, in order to achieve higher data rates. To permit channel estimation at the receiver, the base station transmits cell-specific reference signals (RS), distributed over various resource elements (RE) and over various timeslots[13].
n the UE and sent to the eNodeB in the form of so-called CQIs (Channel Quality Indicator). The quality of the measured sig- nal depends not only on the channel, the noise and the inter- ference level but also on the quality of the receiver, e.g. on the noise figure of the analog front end and performance of the digital signal processing modules. That means a receiver with better front end or more powerful signal processing algo- rithms delivers a higher CQI. The signal quality measure- ments are done using reference symbols. In Figure 2 [15] the whole signal generation chain of the LTEs physical layer with Turbo coding and modulation modules can be seen, which are parts of the link adaptation system.

Fig 2: Signal generation chain in LTE
In the LTE physical layer, resources are managed with the so-called RM Modules (Resource Management), which assign incoming data blocks to resource blocks. One resource block consists of 12 sub-carriers and one time slot. The resource management in LTE can be seen in Figure 3 [15] CQI values are used also to select the optimum resource block i.e. the opti- mum sub-carrier and the optimum time slot.

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change of Transmission mode & CQI. Ideally it seems like the picture below for all channels (PedA, PedB, AWGN)

Throughput at SIM Batch Main



5 CQIS 14

Fig 3: Two dimensional resource management in LTE




2 CQIS 1

1 CQIS 6













Instead of defining propagation models for all possible envi- ronments, ITU proposed a set of test environments in[1] that ade- quately span the all possible operating environments and user mo- bility. In our work we used Pedestrian A, Pedestrian B & Additive White Gaussian Noise(AWGN) Channel.

3.1 ITU Pedestrian A & Pedestrian B Channel

For Pedestrian models the base stations with low anten- nas height are situated outdoors while the pedestrian user are located inside buildings or in open areas. Fading can follow Rayleigh or Rician distribution depending upon the location of the user. The number of taps in case of PedestrianA model is 3 while PedestrianB has 6 taps. The average powers and the relative delays for the taps of multipath channels based on ITU recommendations are given in figure 4 [1].

Fig.4. Average Powers and Relative Delays of ITU multipath
PedestrianA and PedestrianB cases

3.2 AWGN Noise Channel

AWGN is a noise that affects the transmitted signal when it passes through the channel. It contains a uniform continuous frequency spectrum over a particular frequency band.

-15 -10 -5 0 5 10 15 20 25


Fig 5: Ideal variation in throughput with the change of CQI
Here SUMIMO (Single User Multiple Input Multiple Out- put),MUMIMO (Multiple User Multiple Input Multiple Out- put),SUSISO(Single User Single Input Single Output) are used as parameters.
But practically, the variation doesn't happen in this way. The throughput varies differently for each types of transmis- sion mode. Every transmission mode follows a definite rate to vary the parameter (Throughput). We can observe the varia- tion rate through the table below:


4.1 Simulation Result

In LTE we have seen the variation in Throughput with the

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Fig 6: Throughput of all Transmission Modes at CQI 7 (PedA)

Fig 7: Throughput of all Transmission Modes at CQI 7 (PedB)

Fig 8: Throughput of all Transmission Modes at CQI 7 (AWGN)
The variation rate & characteristics' can easily be visual- ized through the figures given below :

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Fig 9: Throughput of all Transmission Modes at CQI 9 (PedA)

Fig 10: Throughput of all Transmission Modes at CQI 9 (PedB)

Fig 11: Throughput of all Transmission Modes at CQI 9 (AWGN)

4.2 Simulation Comparison

From the above figures we have seen that, AWGN Channel gives flat signal and not “frequency-selective” [16] as well. And Pedestrian A channel takes more DB to be stable than Pedes- trian B channel. It can be realized through the picture given below:
Fig 12: Comparison of PedA, PedB & AWGN in TM 342

Fig 13: Comparison of PedA, PedB & AWGN in TM 442
That's why Pedestrian B Channel is effective for the de- veloping countries,who are migrating towards 4G LTE Tech- nology


The analysis done by ITUR showed that evolution of 3G systems to future generation networks will require technology changes on large scale while new quality of service (QoS) re- quirements will require increased transmission bandwidth. So LTE channel models require more bandwidth as compared
to UMTS channel models to account that fact that channel im- pulses are associated to the delay resolution of the receiver.

The LTE channel models developed by 3GPP are 52 based on the

existing 3GPP channel models and ITU channel models. The extended ITU models for LTE were given the name of Extended PedestrianA (EPA), Extended VehicularA (EVA) and Extended TU (ETU). These channel models are classified on the basis of low, medium and high delay spread where low delay spreads are used to model indoor environments with small cell sizes while medium and high delay spreads are used to model urban envi- ronments with large cells.


We would like to thank the whole LTE research group for continuous support and lively discussions. We would also like to thank our supervisor Md. Jakaria Rahimi for his continuous help and support.

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