lte np & perf meas

Long Term Evolution Network Planning and Performance Measurement I. EL-FEGHI ZAKARIA SULIMAN ZUBI A.JAMIL H. ALGABROUN University of Tripoli Computer Science Department University of Tripoli University of Tripoli Facility of Engineering Faculty of Science Facility of Engineering Facility of Engineering Tripoli, Libya Sirte University, Sirte, Libya Tripoli, Libya Tripoli, Libya [email protected] [email protected] [email protected], [email protected]

Abstract:- Data communication is growing rapidly, to keep pace with the increasing demands being placed on mo-bile radio systems, an improved standard was created by the 3rd Generation Partnership Project (3GPP) referred to as Long Term Evolution (LTE) that provides higher throughputs and lower latencies. LTE brings many technical benefits to cellular networks and improves the spectral efficiency in 3G networks, allowing carriers to provide more data and voice services over a given bandwidth. In this work, a detailed LTE radio network dimensioning procedure including frequency, coverage and capacity analysis has been performed in order to prepare a radio planning guideline considering possible network implementation in the city of Tripoli/Libya. At the end, the link level of the LTE network is simulated for both scenarios Uplink and Downlink, to get a closer view to the impact of the Signal to Noise Ratio (SNR) on Bit Error Rate (BER) and Block Error Rate (BLER). Keywords: Long term Evolution, throughputs, latencies, coverage and capacity, SNR, Block Error Rate(BLER) 1. Introduction LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) which was in-troduced in 3rd Generation Partnership Project (3GPP) Release 8. The main advantages with LTE are high throughput, low latency, plug and play, FDD and TDD in the same platform, an improved end-user experience and a simple architecture resulting in low operating costs. LTE downlink transmission scheme is based on Orthogonal Frequency Division Multiple Access (OFDMA) which converts the wide-band frequency selective channel into a set of many at fading sub-channels. The LTE specification provides downlink peak rates of at least 100 Mbps, an uplink of at least 50 Mbps and RAN round-trip times of less than 10ms. LTE supports scalable carrier bandwidths, from 1.4 MHz to 20 MHz and supports both frequency division duplexing (FDD) and time division duplexing (TDD). LTE will also support seamless passing to cell towers with older network technology such as GSM, CDMAOne, W-CDMA (UMTS), and CDMA2000. The next step for LTE evolution is LTE Advanced and is currently being standardized in 3GPP Release 10 [1][2][3].

Radio network planning is a very vital step for a wireless communication technology. As standardiza-tion work of LTE is approaching the end line, it's high time to go for efficient radio network planning guide-line for LTE. For the same reason, along with the fact

that LTE radio network planning work just like other cellular technologies, initial stage planning is normally guided by various industries and vendors at their own discretion. They aren't likely to disclose their advance-ments and findings. That makes the job even more challenging. Whenever new cellular technology is con-sidered for mass deployment hundreds of its RF pa-rameters go through tuning process with a view to find out optimum value. But this phase is time consuming and very costly. So, before commercial deployment if extensive simulation can be run this tuning phase can be facilitated in numerous ways. Cost can also be greatly minimized. That is the benefit of running simu-lation before mass commercial deployment. In Libya, LTE is expected to be commercially launched in Q2 of 2014. All these aim at proper radio network planning of LTE. So, looking for optimizing the vital parameters in the least possible time is a very challenging issue which will obviously help network operators in a greater ex-tent.

The ultimate objective of this work is to come up with the detailed radio network planning guideline with respect to Tripoli city. With this mission ahead, in this paper a step by step method was followed starting from gathering preplanning information which went up to coverage and capacity analysis. For this, the link level simulation had to be performed and link budget had to be prepared. All these have been presented here.

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Prior to that, a brief description of radio network plan-ning methodology has been given.

2. Radio Network Planning Process Radio Network Planning contains number of phases: 1) Site survey-which includes collection of pre-planning information that will be used in the Link Budget prepa-ration and Coverage and Capacity planning calcula-tions. 2) Frequency and spectrum planning- in this phase a variety of parameters' values will be chosen, and according to these parameters the rest of the calcu-lation is processed. 3) Link Budget and Coverage plan-ning, and 4) Capacity planning- these two steps involve propagation model tuning, defining thresholds from Link budget, creating detailed radio plan based on the thresholds, checking network capacity against more detailed traffic estimates, and configuration planning.

2.1 Site Survey The city of Tripoli is located in the North West of the country on the coasted area and centered by longitude line of 13119"E and at latitude line of 32548"N, with population of 2,2 00,000 and having an average building height of 20 meters. The area of Tripoli is 517.6 km2. In this network design, Tripoli has been divided into four main sections according to the popu-lation distribution over the city. These sections are dense urban, urban, suburban, and rural areas. Dense urban is 30.4 km2, Urban is 116.4 km2, and Suburban is 370.8 km2. (Source : HUAWEI ICT Company Libya Branch Office, Date: Jan/2013).

Figure 1 The division of Tripoli, Dense urban is the red area, Urban is the yellow area, Suburban is

the green area

2.2 Frequency and Spectrum Planning In this section, the spectrum is managed; the available frequency band is chosen to be the frequency band for LTE network, the bandwidth, duplex mode, SFR, and Cyclic Prefix are specified also:

Frequency band of 1800 MHz is used. System bandwidth is 20 MHz.

The duplex mode is FDD. Soft frequency reuse of (SFR 1*3*1) is used. Cyclic prefix is chosen to be normal.

2.3 Link Budget and Coverage Planning The link budget calculations estimate the maximum allowed signal attenuation, called path loss, between the mobile and the base station antenna. The maximum path loss allows the maximum cell range to be esti-mated with a suitable propagation model, such as Cost231Hata model. The cell range gives the number of base station sites required to cover the target geo-graphical area. The link budget calculation can also be used to compare the relative coverage of the different systems.

2.3.1 Procedure Link budget and coverage planning is calculated for each scenario separately, for both cases "UL & DL". The procedure steps are [4]:

Step 1: Calculate the Max Allowed Path Loss (MAPL) for DL and UL.

Step 2: Calculate the DL and UL cell radiuses by the propagation model equation and the MAPL.

Step 3: Determine the appropriate cell radius by balancing the DL and UL radiuses.

Step 4: Calculate the site coverage area and the required sites number.

2.4 Capacity Planning With a rough estimation of the cell size and sites count, verification of coverage analysis is carried out for the required capacity. It is verified whether with the given sites density, the system can carry the specified load or new sites have to be added. Theoretical capacity of the network is limited by the number of eNBs installed in the network. Cell capacity in LTE is impacted by sev-eral factors, which includes interference level, packet scheduler implementation and supported modulation and coding schemes [4][5]. Link Budget (Coverage Planning) gives the maximum allowed path loss and the maximum range of the cell, whereas takes into ac-count the interference by providing a suitable model. LTE also exhibits soft capacity like its predecessor 3G systems. Therefore, the increase in interference and noise by increasing the number of users will decrease the cell coverage forcing the cell radius to become smaller. The evaluation of capacity needs the following two tasks to be completed [4]:


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Being able to estimate the cell throughput corre-sponding to the settings used to derive the cell ra-dius.

Analyzing the traffic inputs provided by the opera-tor to derive the traffic demands, which includes the number of subscribers, the traffic mix and data about the geographical spread of subscribers in the deployment area.

2.4.1 Procedure Capacity planning procedure is as follows:

Step 1: calculate the total average throughput per subscriber (UL+DL).

Step 2: calculate the average throughput per subscriber for both UL &DL.

Step 3: calculate the peak and average throughput per site for both UL &DL.

Step 4: determine the maximum number of subscribers per site by calculating the number of subscribers for both UL &DL and taking the lowest one.

Step 5: calculate total sites number required for each scenario.

3. Radio Planning Analysis and Results for Tripoli City

Tripoli is the capital of Libya and it is considered an overpopulated city compared to the rest of most of the country. Efficient radio network planning is obviously a big challenge here with the optimal utilization of lim-ited resources. In this part of the work, coverage analy-sis along with link budget preparation and capacity analysis have been performed. Calculations have been made specifically for Tripoli city. As a result, it can be included for a complete Tripoli city radio network planning, the simulations with a planning tool like Atoll. But this part is here now considered to be the potential future work.

3.1 Link Budget and Coverage Planning Analy-sis

Maximum Allowed Path Loss (MAPL) has different values for dense urban, urban and suburban (UL & DL). So the calculation must be done to every condi-tion and scenario apart, and from these results the cell radius can be calculated for each case. At the end, the minimum cell radius from UL& DL cell radiuses is chosen for each scenario. There are three different cell radiuses, each scenario has its own cell radius. The basic input parameters are as shown in table 1.

TABLE 1 Input parameters for each scenario

Morphol-ogy

Dense urban Urban Suburban

Ch. type UL DL UL DL UL DL Ch. Mod-

el ETU 3 ETU 60 ETU 120

MIMO 1 2

2 2

1 2

2 2

1 2

2 2

Cell Edge Rate

(kbps)

256 1024 256 1024 256 1024

MCS QPSK

3/4

QPSK

1/2

QPSK

3/4

QPSK

1/2

QPSK

3/4

QPSK

1/2

In order to calculate the MAPL; the EIRP, MRRSS, Extra Gain, and Extra Margin and Loss must be calcu-lated first as follows: EIRP = Max Tx Power + Total Tx Gain - Total Tx Loss MRRSS = Rx Sensitivity Total Rx Gain + Total Rx

Loss Extra Gain=Hard Handoff Gain+ MIMO Gain + Other

Gain Extra Margin & Loss = Shadow Fading Margin +

Penetration Loss + Other Loss.

The results are shown in the table 2.

TABLE 2 EIRP, MRRSS, Extra Gain, and Extra Margin and Loss results.

Morphol-ogy

Dense urban Urban Suburban

Channel type

UL DL UL DL UL DL

EIRP per Sub (dBm)

6.19 29.18

6.19 28.68

6.19 28.68

MRRSS (dBm)

- 145.1

8

- 123.

3

- 141.

2

- 121.

3

- 140.

9

- 122.

1 Extra Gain

(dB) 12 9 12 9 12 9

Extra Margin & Loss (dB)

28.43 38.2

5

23.0

4

32.8

3

13.8

1

23.5

9

Then the MAPL is calculated by this equation: MAPL=EIRP - MRRSS + Extra Gain - Extra Margin

& Loss


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MAPL values for each scenario are shown in table 3.

TABLE 3 MAPL values for each scenario

Morphology Dense urban Urban Suburban Ch. type UL DL UL DL UL DL

MAPL (dB) 122.9 124.0 124.4 127.0 133.3 137.0

Using Cost231-Hata model equations, the maximum distance between the terminal and the base station is calculated, which is the cell radius.

Total = L (HSS) + Cm

L = 46.3 + 33.9 log( f ) + 13.82 log(HBS ) + (44.9 - 6.55 log(HSS )) log(d)

(Hss) = 3.2[log (11.75 )Hss]^2 - 4.97 For Urban areas

(Hss) = [1.1log (f) - 0.7]Hss - [1.56log(f) - 0.8] For Suburban or Rural areas

The resulted cell radiuses after the balancing are shown in Table 4.

TABLE 4 Cell Radius values for each scenario

Morphology Dense urban

Urban Suburban

Cell Radius (Km)

0.33 0.46 1.49

After determining the cell radius for each scenario, sites number and sites coverage areas are calculated by the equations below:

Site coverage area =

Required sites number =

Dense Urban: Site Cov. Area = 0.2122 km2, Required Sites No. = 144 site Urban:

Site Cov. Area = 0.412 km2, Required Sites No. = 283 site Sub Urban:

Site Cov. Area = 4.326 km2, Required Sites No. = 86 site

3.2 Capacity Planning Analysis Three types of service packages are provided, golden service package, silver service package, and bronze service package, each service has its own quality the month service package, the DL and UL peak data rates, and the package percentage- all of these characteristics are shown in table 5.

The traffic ratio of the UL and DL in terms of the total traffic is chosen to be 20% for UL and 80% for DL. The number of subscribers must be specified in order to continue the analysis, the subscribers number for Dens Urban is considered to be 500,000, for Urban 300,000, and for Sub Urban 200,000, so that the total number of subscribers is 1,000,000.

TABLE 5 The different provided services

Data card

package Type

Month service package

(GB)

DL peak rate kb/s

UL peak rate kb/s

Package percent-

age

Gold 20 2048 1024 10% Sliver 15 2048 512 50% Bronze 10 1024 256 40%

Firstly the total average throughput per subscriber must be calculated in order to calculate the average through-put per site. Avg. throughput per sub in BH (DL+UL) (Kbps) = Month service package Usage ratio for service pack-

age BH convergence ratio 1000 1000

Total avg. throughput per sub in BH = (Avg. throughput per sub in BH (DL+UL) packet percent-

age)

TABLE 6 Total average throughput per subscriber in BH

Data card package Type

Average throughput /user in BH

(Kbps)(DL+UL) Gold 88.89 Sliver 66.67

Bronze 44.44 Total 60


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Avg. throughput per subscriber for UL = Total avg. throughput per sub (UL +DL)

UL traffic ratio Avg. throughput per subscriber for DL = Total avg.

throughput per sub (UL +DL) DL traffic ratio

Table 7 shows the results of Average throughput per subscriber calculation for each (UL &DL).

TABLE 7 Average throughput per subscriber for UL & DL

Chanel Type

Total avg. throughput per sub (UL +DL)

(Kbps)

Traffic ratio

Avg. throughput

per sub-scriber (Kbps)

UL 62.91 20% 12 DL 62.91 80% 48

Then the peak and average throughputs per site for both UL and DL must be calculated.

Peak throughput per site =(data RE/sec bits per RE MIMO effect coding rate)

Average throughput per site = (peak throughput per modulation scheme sub number percentage)

The average throughput per site is shown in table 8.

TABLE 8 Average throughput per site

Avg. throughput per site

(Mbps)

DL UL

112

40

Now, the maximum subscribers number per site is cal-culated for UL and DL and the lowest is chosen.

Max Sub No. per site =

Max Sub number per site (DL) = 2333 sub/site Max Sub number per site (UL) =3333 sub/site

Then the total number of sites according to the capacity planning analysis is calculated.

Total sites number =

Dense Urban:

Total sites number = 215 site Urban:

Total sites number = 129 site Sub Urban:

Total sites number = 86 site

The required sites number for a specific area should be chosen to be the maximum number of sites obtained from coverage and capacity planning calculations to satisfy the traffic requirements of both coverage and capacity; according to the results obtained from the coverage and capacity planning analysis, the final sites number required for each scenario are shown in table 9.

TABLE 9 The final required sites number for each scenario

Scenario Required Sites Number

Dense urban

215

Urban 283 Suburban 86

4. PERFORMANCE MEASUREMENT FOR THE LINK LEVEL OF AN LTE NETWORK

The performance of the link level and communication quality in terms of bit error rate (BER) or block error rate (BLER) can be expressed as a function of the sig-nal-to-noise ratio (SNR), or the signal to-interference ratio (SIR), depending on which type of signal distur-bance is dominant. In digital transmission, the number of bit errors is the number of received bits of a data stream over a communication channel that have been altered due to noise, interference, distortion or bit syn-chronization errors. In this section a simulation of the channels between the transmitter (eNB or UE) and the receiver (eNB or UE) is done to know how the BER and BLER are related to the SNR, also to get a clear view to the spectrum of the transmitted signal, at the transmitter and the receiver. To perform this simulation, ADS2009 (Advanced De-sign System 2009) simulation program is used.

4.1 Downlink(DL) with FDD propagation mode, at the receiver(Rx)


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Some cases are illustrated in this paper. For the first case, the channel between the transmitter (eNB) and the receiver (UE) is simulated for DL scenario, the propa-gation mode applied is FDD, and all the results are taken at the receiver (UE) end. The plots that include

the resulted BER and BLER and how they affect the SNR are shown in Fig-ure 2.

Figure 2 BER&BLERvsSNR for DL-Fading

4.2 Uplink(UL) with FDD Propagation Mode, at the Receiver(Rx)

In this case the channel between the transmitter (UE) and the receiver (eNB) was simulated for UL scenario, the propagation mode applied is FDD, and the results are taken at the receiver (eNB) end. The plots that include the resulted BER and BLER and how they affect the SNR are shown in Figures 3.

Figure 3 BER&BLERvsSNR for UL-AWGN

5. Conclusions A solution to improve the current communication sys-tem in Tripoli city is introduced by designing an LTE

radio network taking into consideration the possibility of maintaining the current 3G network at the very low populated areas the rural areas. The outcome as shown in fig.4 of the network planning design is as follows: The peak throughput/site for the DL is 144 Mbps. The peak throughput/site for the UL is 50.4 Mbps. The average throughput/site for the DL is 112

Mbps. The average throughput/site for the UL is 40

Mbps. The max. Subs. No./site was found to be 2333

sub/site.

The total sites number for each scenario apart; for dense urban 215 sites, for urban 283 sites, and for sub-urban 86 site.

From the link level -of the LTE network- simulation cases, we see that as the BER or BLER increases, the SNR decreases, and vice versa. The relation of BERvsSNR and BLERvsSNR varies depending on many parameters such as: modulation scheme, code rate, channel type, and antenna configuration. The main observations are summarized in the following points: From the results it is shown that the BER&BLER

can get improved by increasing the number of re-ceiving antennas (antenna diversity improve-ment).

The number of transmitting antennas doesnt af-fect the BER or BLER values.

The resulting BER&BLER from TDD and FDD simulation cases have the same performance for the same antenna configuration.

Receiver diversity affects the SNR; SIMO (1x2) antenna configuration increases the SNR by 3dB whereas MIMO (2x2) increases the SNR by 4dB.

For the future work, its recommended to include the rest of the country in the network planning, including the rural areas. Its also highly recommended to use a planning tool like Atoll, the planning tool will save the time and effort and will make the calculations more accurate. Such planning tools are so expensive and thats why in our work it was impossible to use it.

Reference

[1] M. Junaid Arshad, Amjad Farooq, Abad Shah, "Evolution and Development towards 4th Generation

Figure 4. The peak throughputs


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(4G) Mobile Communication Systems", Journal of American Science, 2010; 6(12).

[2] Harri Holma, Antti Toskala, "LTE for UMTS OFDMA and SC-FDMA Based Radio Access", John Wiley & Sons, Ltd, both of Nokia Siemens Networks, Finland, 2009.

[3] Ericsson, Long Term Evolution (LTE), an intro-duction, October 2007.

[4] HUAWEI TECHNOLOGIES, Long Term Evolu-tion (LTE) Radio Access Network Planning Guide CO., LTD.

[5] Abdul Basit, Syed, Dimensioning of LTE Network,Description of Models and Tool, Coverage and Capac-ity Estimation of 3GPP Long Term Evolution radio in-terface, February 2009.


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lte np & perf meas

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