Comparison between UMTS/HSPA+ and WiMAX/ IEEE 802.16e in Mobility Scenarios Ricardo F. Preguiça, Luís M. Correia Instituto Superior Técnico / Instituto de Telecomunicações Technical University of Lisbon, Lisbon, Portugal ricardopreguica@hotmail.com, luis.correia@lx.it.pt Abstract The main purpose of this work was to compare the performance of HSPA+ and Mobile WiMAX. Two scenarios were considered: single and multiple users. In the single user scenario, only one user is placed in the cell requesting a certain throughput, and then the maximum distance to the base station for the requested application throughput is calculated. Afterwards, the model was adapted to a multiple user and multiple services scenario, a more realistic approach. A simulator was developed to obtain the analysis of the network for several parameters in an urban scenario with variable slow and fast fading margins. The results for single user model show that, in an indoor scenario, HSPA+ can serve 14.4 Mbps up to 0.17 km, in downlink, and 7.2 Mbps up to 0.05 km, in uplink. Still considering an indoor scenario, Mobile WiMAX can serve 14.4 Mbps up to 0.04 km, in downlink, and 7.2 Mbps up to 0.02 km in uplink. Considering the multiple users scenario, HSPA+ presents better results than Mobile WiMAX, both for downlink and uplink, regarding average network throughput and number of served users, because of its higher coverage. As for the network radius, the results are similar. Keywords: UMTS, HSPA+, Mobile WiMAX, Capacity, Coverage, Multi-Service. C I. ITRODUCTIO urrently, third generation (3G) systems, e.g., the Universal Mobile Telecommunications System (UMTS), are designed for multimedia communication: with these, person-to-person communication can be enhanced with highquality images and video, and access to information and services on public and private networks will be improved by the higher data rates and new flexible communication capabilities of 3G systems [1]. Many new services are based on multimedia applications, such as Voice over Internet Protocol (VoIP), video conferencing, Video on Demand (VoD), massive online games, and Peer-to-Peer (P2P) [2]. In standardisation for a Wideband Code Division Multiple Access (WCDMA) has emerged as the most widely adopted 3G air interface. Its specification has been created in the 3rd Generation Partnership Project (3GPP), which is also responsible for important evolution steps on top of WCDMA: High Speed Packet Access (HSPA) for downlink (DL) in Release 5 and uplink (UL) in Release 6. The DL solution, High Speed Downlink Packet Access (HSDPA) was Carlos Caseiro Vodafone Lisbon, Portugal Carlos.Caseiro@vodafone.com commercially deployed in 2005 and the UL counterpart, High Speed Uplink Packet Access (HSUPA), during 2007. The initial peak data rate of HSDPA was 1.4 Mbps but, by the end of 2007, 7.2 Mbps were available, with the peak data rate of 14.4 Mbps foreseen for a near future, starting the mobile Internet Protocol (IP) revolution [3]. HSUPA started to be deployed at the end of 2007, with peak data rates of 1.4 Mbps, being expectable that the maximum peak data rate is around 6.0 Mbps. Furthermore, Release 7, also known as HSPA Evolution or HSPA+, has its commercial deployment foreseen for 2009 [3]. The HSPA+ is currently also being standardised by 3GPP in Release 8. HSPA+ offers a number of enhancements, providing major improvements to end-user performance and network efficiency. The aim of Release 7 is to further improve the performance of WCDMA through higher peak data rates, lower latency, greater capacity and increased battery time. Multiple Input Multiple Output (MIMO) and Higher Order Modulation (HOM) extend the peak data rate to 43.2 Mbps in the DL and 11.5 Mbps in the UL, [4] and [5]. Worldwide Interoperability or Microwave Access (WiMAX) is an emerging wireless communication system that can provide broadband access with large-scale coverage, supporting fixed and mobile accesses. The former is based on Institute of Electrical and Electronics Engineers (IEEE) 802.16-2004, published in April 2002, and is optimised for fixed and nomadic access. The latter is designed to support portability and mobility, being based on the IEEE 802.16e amendment to the standard that provides Wireless Metropolitan Area etwork (WMA). IEEE 802.16.e, released in February 2006, offers improved support for MIMO and Adaptive Antenna Systems (AAS), as well as hard and soft handovers. Mobile WiMAX certifications profiles are for the Time Division Duplex (TDD) mode, which enables to adjust the DL/UL ratio to efficiently support asymmetric traffic [6]. Mobile WiMAX is a Broadband Wireless Access (BWA) solution that enables convergence of mobile and fixed networks, through a common wide area broadband radio access technology and flexible network architecture. The Mobile WiMAX Air Interface adopts Orthogonal Frequency Division Multiple Access (OFDMA) for improved multi-path performance in on Line of Sight (LoS). Scalable OFDMA
(SOFDMA) is introduced in IEEE 802.16e, to support scalable channel bandwidths from 1.25 to 20 MHz. The use of Adaptive Modulation and Coding (AMC) allows WiMAX to support different modulations and adaptively to exploit highest available data rate based on link quality. The system offers scalability in both radio access technology and network architecture, thus, providing a great deal of flexibility in network deployment options and service offerings. The features supported by Mobile WiMAX enable the technology to support peak DL data rates up to 63 Mbps per sector, and UL ones to 28 Mbps per sector, in a 10 MHz channel. Regarding Quality of Service (QoS), sub-channelisation and Media Access Protocol (MAP) bases signalling schemes provide a flexible mechanism for optimal scheduling of space, frequency and time [6]. In October 2007, Radiocommunication Sector of the International Telecommunications Union (ITU-R) approved the inclusion of WiMAX in the International Mobile Telecommunications (IMT-2000) set of standards. This decision escalates opportunities for global deployment, especially within the 2.5-2.69 GHz band, to deliver Mobile Internet to satisfy both rural and urban market demand [7]. Both HSPA+ and Mobile WiMAX technologies are being developed simultaneously which makes possible to believe that Mobile WiMAX services will also complement existent and future broadband technologies, both wired and wireless, to best assure the coverage and capacity requirement of consumers [8]. This work was made in collaboration with the mobile operator Vodafone. Several technical details were discussed with the company. The type and content of the results analysis had also been discussed, with the presented analysis being the ones that fit better the aim of this work, therefore, providing the most relevant results. In Section II the models for the theoretical calculations are described. The default scenario is presented and analyzed in Section III both for DL and UL. In Section IV the main conclusions are drawn. II. THEORETICAL MODELS To assess HSPA+ and Mobile WiMAX capacity and coverage, in DL and UL, two models were developed: the single user model and the multiple users one. The first one is intended to assess the maximum cell radius in a single user scenario, and can be used in the first phase of network planning to estimate cell radius, whereas the second is intended to study HSPA+ and Mobile WiMAX performance with the objective of analysing a more realistic scenario, with users performing multiple services, being randomly spread over the coverage area of base station (BS), similar to the ones in real networks. A. Single User The HSPA+ single user model was developed, allowing calculating the maximum cell radius according to several system parameters, as the desired throughput, the antenna configuration, modulation scheme, type of scenarios and overheads, among others. For Mobile WiMAX, the same approach was followed, but in this case were added some parameters such as TDD Split and channel bandwidth. The same expression is used for both HSPA+ and Mobile WiMAX cell radius calculation, the difference being the calculation of the receiver s sensitivity. For HSPA+ DL and HSPA+ UL, the available throughput is calculated based on the SR and E c / 0 curves in [4] and [5], whereas, for Mobile WiMAX, the available throughput is calculated based in the tables of physical throughputs for different code rates, modulation, TDD Split DL:UL and Signal-to-oise Ratio (SR) values from [6]. The path loss is calculated using the link budget detailed in [9]. From the COST-231 Walfisch-Ikegami propagation model, one has [10]: L L L L EIRP P G M, (1) p[db] 0[dB] tt[db] tm[db] [dbm] r [dbm ] r [dbi] L 0 :free space loss; L tt : rooftop-to-street diffraction loss; L tm : approximation for the multiscreen diffraction loss; EIRP: equivalent isotropic radiated power; P r : available receiving power at the antenna port; G r : receiving antenna gain; M: total margin, described in [9]. Finally, from the COST-231 Walfisch-Ikegami model, the cell radius can be calculated by: [km] ' ' EIRP[dBm] Pr G [dbm] r M [dbi] [db] Ltt L [db] tm L [db] 0[dB] 20 kd R 10, (2) L L k log( d ) ; ' tt tt d [km] k d : dependence of the multiscreen diffraction loss versus distance; d: distance between the user and the ode B; ' L L 20 log( d ) ; 0 0 [km] R: maximum cell radius. B. Multiple Users The multiple users simulator was adapted from the one developed in [9]. ew HSPA+ and Mobile WiMAX modules were added, both for DL and UL, while the main structure was left unchanged. The HSPA+ and Mobile WiMAX modules main objectives are the analysis of the network capacity and coverage, through a snapshot approach, calculating instantaneous network results such as radius, number of users per BS and total throughput. These modules perform analysis on a BS basis, being executed in all BSs in the network. In these simulations, the city of Lisbon was chosen, considering 194 BSs and 1600 users spread non-uniformly. Afterwards, the modules compute averages regarding some of the parameters recorded for each BS, and extrapolate some results for the busy hour analysis. When the offered traffic exceeds the BS s capacity, 43.2 and 41.5 Mbps for HSPA+ DL and Mobile WiMAX DL, three reduction strategies, with different QoS requirements, were adapted from [11] and [12]. In terms of definition of maximum throughput supported, for HSPA+, MIMO 2 2 configuration and 64 Quadrature Amplitude Modulation [db]
(64QAM) modulation are used while for Mobile WiMAX a TDD 3:1 is considered with MIMO being applied with the use of Relative MIMO Gain (RMG) [13] model due to the lack of more realistic curves. For UL, the BS s capacity considered was 11.5 Mbps for HSPA+ and 7.2 Mbps for Mobile WiMAX, not considering neither MIMO nor 64QAM. One of the main difference between the single model and the multiple users model is the introduction of the interference margin, which is a parameter used to emulate the load in the cell. The interference margin calculation is described in detail in [14]. Due to the interference margin, the path loss decreases, leading to a lower cell radius or throughput, depending on the analysis, when one compares the single user with the multiple users scenarios. The same approach was taken for both HSPA+ and Mobile WiMAX. The distributions assumed for the slow and fast fading margins considered are the Log-ormal and the Rayleigh, respectively. The standard deviations considered are referred in [14]. The user is connected to the closest BS. ext, the throughput associated to the user distance is calculated, i.e., the maximum throughput that the BS can offer to the user, considering the path loss. For HSPA+ DL, the SR is given by: SR P G EIRP L G L G, (3) [db] Rx [dbm] [dbm] p [db] [dbm] P[dB] r[dbi] u[db] [dbm] p [db] SR: signal to noise ratio; P Rx : received power at receiver input; : total noise power; G p : processing gain; L u : user losses. For HSPA+ UL, the user losses are replaced by the cable losses, L c. SR is mapped onto throughput, this algorithm being explained in detail in [14]. The received power, for both systems. after the path loss calculation, is calculated, for DL, by: P EIRP L G L (4) RX [dbm] [dbm ] P[dB] r[dbi] u[db] For UL, the user losses are replaced by the cable losses, L c. Afterwards, for Mobile WiMAX. the received power value is compared with different receiver sensitivities of Mobile WiMAX, Table I, being chosen the respective SR that corresponds to a better approximation. One should notice that, in Mobile WiMAX, the SR value, and therefore the modulation used, are associated to the user s distance and, as a consequence, with the power at receiver. The value of SR is used in the calculation of the number of data sub-carriers, DSC, for DL by: DSC TSC 24 16 10 ( Prx [dbm] 114 SR[dB] IM F[dB] ) 10 F S[MHz] (5) TABLE I. RECEIVER SESITIVITY FOR EACH VALUE OF SR FOR 5, 10 AD 20 MHZ CHAELS. Receiver Sensitivity [dbm] SR [db] 5 MHz 10 MHz 20 MHz DL UL DL UL DL UL 8-92.20-95.88-86.23-89.65-80.29-83.71 10.5-89.70-93.38-83.73-87.15-77.79-81.21 14-86.20-89.88-80.23-83.65-74.29-77.71 16-84.20-87.88-78.23-81.65-72.29-75.71 18-82.20-85.88-76.23-79.65-70.29-73.71 20-80.20-83.88-74.23-77.65-68.29-71.71 For UL, the number of sub-carriers is calculated by: DSC TSC ( Prx [dbm] 114 SR[dB] IM F[dB] ) 2 10 16 10 F S[MHz] TSC : total number of sub-carriers; F S : sampling frequency; I M : implementation margin; F : noise figure. The user physical throughput, due to the distance to BS, is given by[15]: PHY DSC SB DS Rb [bps] (7) T F[s] β: effective code rate; DS : number of OFDM data symbols considering the TDD split adapted; SB : number of symbol bits; T F : frame duration. In UMTS/HSPA+, the operators have two carriers, one dedicated for Release 99 and the other to HSPA+. Services like voice and video-telephony are served by the Release 99 carrier in dedicated channels and the data services are transported by the HSPA+ carrier in such a way that, only data services contribute to the capacity of HSPA+. Mobile WiMAX, instead of UMTS, has an available bandwidth for all services which makes that voice and video-telephony services, in spite of not being analysed together with data services, have to be performed and, occupying the bandwidth, are reducing the available capacity for data services. The calculation of the cell radius in the multiple users simulator is obtained by a different approach from the one used in the single user model. In the multiple users scenario, the cell radius is defined as the distance of the user served further away from the BS. For the network, the most important parameters are the average network radius, r net, the average satisfaction grade, S Gnet, the average ratio of served users, S u network throughput, R bnet. The average network radius, r net : (6), and the average
BS r j rnet r: BS cell radius, BS : number of active BSs. The average satisfaction grade, S Gnet : BS BS SGnet (9) BS S G : satisfaction grade of a BS, being the ratio between the total served throughput and the total requested throughput. The average ratio of served users, S U : BS S Gj ubs j SU utot ubs : number of users served in a BS. utot : total number of covered users. The average network throughput, R BS R bnet bbsj[mbps], is given by: Rbnet BS R bbs : instantaneous served throughput in a BS. (8) (10) (11) The network dimensioning takes the capacity and coverage aspects into account for the busy hour of the day, i.e., the most exigent period of the day when the probabilities of congestion are higher. Bearing this in mind, the number of users, served in a hour, uhnet,, and the total network traffic, T net, are calculated by: uhnet BS (12) net[gb/h] BS uhbs T T (13) BS[GB/h] uhbs : number of users per hour in a BS. III. RESULTS AALYSIS A. Scenarios Two different scenarios are considered with different purposes. The single user scenario is developed considering that the cell is composed by only one user which has all available resources allocated to it. For a certain service characterised by a throughput, the maximum cell radius is calculated. When using the single user scenario, all existent multipaths are considered completely uncorrelated with the objective of apply the maximum MIMO gains. The multiple users scenario contemplates the existence of several users uniformly distributed along the coverage area of the BS and performing different services with different associated throughputs. The environments considered for both scenarios are pedestrian, vehicular, and indoor. In single user scenario, these environments are distinguished by the different values of the slow and fast fading margins as well as the indoor attenuation. For the multiple users scenario, the indoor environments represent the largest percentage of the overall users as it is, at the present, the most common environment for users performing the types of services analysed, mainly associated to laptops. In the multiple users scenario, the slow and fast fadings are statistical distributed by a Log-ormal and a Rayleigh, respectively. In terms of antenna configuration, besides Single Input Single Output (SISO), diversity is applied in Single Input Multiple Output (SIMO). MIMO is another configuration considered. For the multiple users scenario, seven services with different QoS classes were considered. The penetration percentages of the Voice Centric profile considered, as well as the QoS priority, according to which the services are reduced, are presented in Table II. For the QoS priority list, the first services to be reduced are the ones with higher QoS value. TABLE II. PEETRATIO PERCETAGE AD QOS PRIORITY. Service Penetration Percentage [%] QoS Voice 48.6 1 Video Telephony 0.2 2 Streaming 7.1 4 FTP 16.9 7 Web 11.8 3 Email 10.5 5 MMS 4.9 6 The maximum and minimum throughput values for the services considered in the default multiple users scenario, in UL and DL, are presented in Table III. The values are common for HSPA+ and Mobile WiMAX. The parameters for the link budget estimation used and the default values considered, are the ones listed in Table IV and Table V, based in [9] and [14]. The BS antenna gain is 17 dbi, with a 65º half power beam width radiation pattern detailed in [9]. The HSPA+ and Mobile WiMAX traffic models characterisation are detailed in [14] with no differentiation between the two systems. For Web and Streaming, the most asymmetric services, the volume associated to UL traffic is lower because corresponds to signalling and control processes. With respect to volume, the FTP and streaming are the services which sessions have a higher volume associated. On
average, the volume for Email and MMS are considered similar bur Email have a higher requested throughput. In terms of session duration, it depends on the requested throughput and on other parameters like the average page reading time in Web service. TABLE III. Service MIIMUM AD MAXIMUM THROUGHPUTS FOR HSPA+ AD MOBILE WIMAX. Maximum Throughput [Mbps] Minimum Throughput [Mbps] DL UL DL UL Voice 0.0122 0.0122 VT 0.064 0.064 Streaming 3.6 0.512 0.512 FTP 10.0 3.6 1.024 HTTP/Web 7.2 3.6 1.024 E-mail 3.6 1.024 MMS 0.512 0.128 TABLE IV. DEFAULT HSPA LIK BUDGET VALUES. Parameter HSPA+ DL HSPA+ UL BS DL Transmission Power [dbm] 44.7 --- MT Transmission Power [dbm] --- 24 Frequency [MHz] 2142.5 1952.5 Modulation 64QAM 16QAM Configuration MIMO (Dedicated) MT Antenna Gain [dbi] 0 Maximum BS Antenna Gain [dbi] 17 User Losses [db] 1 Cable losses between emitter and antenna [db] 3 SIMO oise Figure [db] 9 5 Diversity Gain [db] --- 2 Interference Margin [db] 6 Total Percentage of power for signalling and control (Release 99 + HSPA) [%] Reduction Strategy 25 15 QoS Class Reduction Service throughput reference [Mbps] 7.2 3.6 The higher throughputs considered reflect the strong trend of requesting, by part of users, of applications more demanding in terms of networks capacity. Voice and Video- Telephony throughputs are not modified, when compared with the present technology, because an eventual improvement does not cause perceptible advantages to the users. TABLE V. DEFAULT MOBILE WIMAX LIK BUDGET VALUES. Parameter Mobile WiMAX DL Mobile WiMAX UL BS DL Transmission Power [dbm] 43 --- MT UL Maximum Power [dbm] --- 23 TDD split 3:1 1:1 Frequency [GHz] 2.5 Channel Bandwidth [MHz] 10 Modulations Configuration QPSK 16QAM 64QAM MIMO (Dedicated) QPSK 16QAM SIMO MT Antenna Gain [dbi] -1 Maximum BS Antenna Gain [dbi] 17 Cable losses between emitter and antenna [db] 0.7 User Losses [db] 1 oise Figure + Implementation margin [db] 8 5 Diversity Gain [db] 3 Interference margin [db] 2 3 Percentage of signalling and control power [%] Reduction Strategy 0 0 QoS Class Reduction Service throughput reference [Mbps] 7.2 3.6 B. Results In this section, the main results are presented, with additional results being found in [14]. The objective is to evaluate HSPA+ and Mobile WiMAX capacity and coverage and compare them. Firstly, the results for single user scenario are analysed. Once the single user scenario is a more controlled scenario, the overheads considered are different for both systems and the throughputs analysed in the single user scenario are the ones at application level. The parameters for HSPA+ are established such as MIMO and SIMO configurations and 16QAM and 64QAM modulations, for UL and DL respectively, which allow a reasonable range of values of throughput for a context of single user. ote that, if the default parameters for multiple users scenarios are used in this context, the capacity of the BS will be excessive and improperly for a unique user performing a certain service. With the purpose of comparing the same values of throughputs, a several set of parameters is set up for Mobile WiMAX such as TDD Split 3:1 and 1:1, for DL and UL respectively, SISO configuration and a channel bandwidth of 10 MHz. With regard to modulation, due to AMC, it can be changed for obtain a certain throughput. In the comparison performed, Quaternary Phase Shift Keying (QPSK) and 16QAM are enough to reach demanding throughputs. Concerning the environment, since its variation has the consequences studied in [14], the pedestrian one was chosen in order to reach higher coverage of the cell. The cell radii obtained for different throughputs, in a pedestrian environment, are shown in Fig. 1.
the slow and fast fading does not cause excessive impact for shorter distances. Figure 1. HSPA+ and Mobile WiMAX maximum cell radii for different throughputs for the pedestrian environment. Regarding DL, with a HSPA+ system, the cell radius varies from 1.34 km, for 6.0 Mbps, to 0.72 km, for 17.0 Mbps, which represents a decrease of 46%. In Mobile WiMAX, the variation observed is not so noticeable, being from 0.27 km to 0.16 km for the same interval of throughputs, establishing a reduction of 41%. The ratio between the HSPA+ and the Mobile WiMAX radii decreases from 5.0 to 4.6, which indicates that differences occurred are slightly minimised for higher throughputs. Concerning UL, the interval of throughputs values analysed is between 3.5 and 7.6 Mbps. In a HSPA+ system, the radius for 3.5 Mbps is 0.28 km and the lower radius achieved is 0.17 km. In Mobile WiMAX, the cell radius varies from 0.17 to near 0.09 km considering the same interval. ote that the lowest radius in HSPA+ is similar to the highest radius of Mobile WiMAX which confirms the advantage of using HSPA+ when the coverage aspects are fundamental. Instead of DL, the ratio between the radii for two systems is not so notorious in UL: 1.7 for a throughput of 3.5 Mbps and 1.8 for the upper limit of the interval. In the multiple users simulator, several parameters were evaluated. The parameters chosen to analyse both capacity and coverage of the systems were the average network radius, the average satisfaction grade, the average ratio of served users, and the average network throughput. The results associated to the busy hour extrapolation are also referred when necessary. The results compared include only the data services once in HSPA+ the voice and video-telephony are served by the Release 99 carrier. The location of BSs for both systems is common. In Fig. 2, the comparison of the dependence of the instantaneous user throughput with the distance for both HSPA+ and Mobile WiMAX is presented for DL. For Mobile WiMAX, voice and video-telephony users are included in this analysis. As expected, due to the conclusions in single user analysis, HSPA+, when compared to Mobile WiMAX, can serve users placed farther away, having the capability to cover a larger area of Lisbon. The instantaneous throughput decreases with distance, because the influence of the interference margins as Figure 2. HSPA+ and Mobile WiMAX DL instantaneous throughput for all users depending on the distance. The average network throughput for DL, Fig.3, is higher in HSPA+ than Mobile WiMAX. The difference is significantly: 8.85 Mbps for HSPA+ and only 3.26 Mbps when considering Mobile WiMAX. In this context, one should also notice that the average number of users per BS is 3.2 and 1.8 for HSPA+ and Mobile WiMAX, respectively. These results are a consequence of the larger coverage that HSPA+ can provide. HSPA+ covers all the users placed in Lisbon, whereas Mobile WiMAX covers near half of total effective users. With respect to the DL average ratio of served users, Fig.4, Mobile WiMAX can serve 68% of the covered users and HSPA+ 64%, which means that more users covered by Mobile WiMAX are associated to SR values above the threshold for the minimum throughput that is the limiting factor for this case. Although Mobile WiMAX has a higher average of ratio users, the trade-off of number of covered users and the average ratio of served users is advantageous for HSPA+ that, in absolute values, serves more users. The reduction strategies are not so important once the number of users is insufficient to exceed the maximum capacity of the BS. Figure 3. HSPA+ and Mobile WiMAX DL average network throughput. Concerning the average satisfaction grade for both systems, Fig.5, the results show that HSPA+ users are served with higher average satisfaction grade, 0.95, than the 0.85 verified for Mobile WiMAX, which means that the requested throughput, for HSPA+, is almost similar to the served one.
Figure 7. HSPA+ and Mobile WiMAX DL total number of users per hour. Figure 4. HSPA+ and Mobile WiMAX DL average ratio of served users. Figure 8. HSPA+ and Mobile WiMAX DL total network traffic. Figure 5. HSPA+ and Mobile WiMAX DL average satisfaction grade. The average DL network radius for HSPA+ is approximately 0.30 km and for Mobile WiMAX is near to 0.12 km, Fig.6. These results are consequence of the results of single user. Moreover, for higher distances, the SR values are lower and the influence of the variable slow and fast fading are more noticeable. Concerning the UL, the variation of the instantaneous user throughput with the distance, Fig.9, is almost similar to the DL one. In HSPA+, there are users placed far away from the BS of 0.2 km and, for Mobile WiMAX, the highest distance observed is 0.13 km, demonstrating that the coverage is lower for Mobile WiMAX. For UL, there are limitations inherent to the MT as the transmission power which decreases the average radii when compared to DL. Figure 6. HSPA+ and Mobile WiMAX DL average network radius. Still considering DL, the influence of the higher average throughput in HSPA+ is noticed in Fig. 7, where it is possible to observe the total number of users per hour for both systems. HSPA+ presents a larger number of users served within the hour period, approximately 250 000 users, and Mobile WiMAX around 120 000 users. The users served in an hour, as seen in Fig. 8, transferred total network traffic of 450 GB/h in HSPA+, the triple verified for Mobile WiMAX. Figure 9. HSPA+ and Mobile WiMAX UL instantaneous throughput for all users depending on the distance. The UL average network throughput, for both systems is presented in Fig.10. For HSPA+, the average network throughput is 1.90 Mbps while for Mobile WiMAX is around 1.08 Mbps, representing a decrease of 43%. One must have in mind that, for the calculation of this parameter, only the BSs active are keeping in account. Underlying to this analysis, one should notice that in HSPA+, in average, 60 BSs are active while in Mobile WiMAX number is reduced to 25. Moreover, the percentage of covered users is 43% and 13% for HSPA+ and Mobile WiMAX, respectively.
consequence of the higher HSPA+ coverage verified for a single user scenario which makes possible that users further away from the BS are served in HSPA+, Fig.13. Figure 10. HSPA+ UL and Mobile WiMAX UL average network throughput. With respect to the UL average ratio of served users, Fig.11, Mobile WiMAX can serve 28% of the covered users and HSPA+ 23% which means that more users covered by Mobile WiMAX have SR values above the threshold for the minimum throughput that is the limiting factor for this case. Although Mobile WiMAX has a higher average of ratio users, as happens in DL, the trade-off of number of covered users and the average ratio of served users is advantageous for HSPA+ that, in absolute values, serve more users. The reduction strategies are not so important once the number of users is, generally, insufficient to exceed the maximum capacity of the BS. Figure 12. HSPA+ and Mobile WiMAX UL average satisfaction grade. Figure 13. HSPA+ and Mobile WiMAX UL average network radius. Figure 11. HSPA+ and Mobile WiMAX UL average of ratio of served users. In Mobile WiMAX, one can notice that its UL average satisfaction grade, 0.89, is slightly lower than the obtained with HSPA+, near to 0.95, corresponding to a reduction of 7%, Fig.12. In HSPA+, the differences between the served throughput and the requested one are almost imperceptible. One should also notice that the average satisfaction grade evaluation takes all the services into account. Bearing this in mind, the percentages of served users performing Web and FTP, for instance, are 24.6% and 32% of the total data services users, i.e., excluding voice and video-telephony, in HSPA+ while, for Mobile WiMAX, the percentages mentioned decay for 17.9% and 19.7%. These percentage means that HSPA+ has the capability of serve users performing more demanding services with a higher average satisfaction grade than Mobile WiMAX users. Therefore, and in a instantaneously perspective per user, HSPA+ also presents better results with 1.4 Mbps, more 0.45 Mbps than a user being served by Mobile WiMAX. HSPA+ presents a larger UL average network radius than Mobile WiMAX, 0.10 km, representing an increase of 61% when compared to the latter, near to 0.06 km. These results are One can observe that, for UL, HSPA+ can serve more users in the hour period than Mobile WiMAX, Fig.14. This happens because de trade-off of covered users and percentage of served users is beneficial to HSPA+. Moreover, the average instantaneous throughput are also higher for HSPA+, due to its higher satisfaction grade and because the services more demanding have also higher penetration, which means that each session is realized in a shorter interval of time. Therefore, HSPA+ serves 45 800 users, more 13 800 than Mobile WiMAX. Figure 14. HSPA+ and Mobile WiMAX UL number of users per hour. The total UL network traffic, Fig.15, depends, essentially, on the number of users in an hour and the percentage of served traffic for each service. HSPA+ serve more users and its distribution of services include more users performing sessions associated to large volume of traffic such as FTP and Web. So, as expected, HSPA+, for the total network traffic presents 34 GB/h, while Mobile WiMAX results, for the same parameter, go to up 23 GB/h.
Additional results regarding the default scenario, as well as the results for other scenarios with several modifications and impact studies are presented in [14]. Figure 15. HSPA+ and Mobile WiMAX UL total network traffic. IV. COCLUSIOS This paper deals with the comparison of HSPA+ and Mobile WiMAX when deployed together, with BSs with some location, focusing on capacity and coverage aspects, considering equal conditions, as the number of users offering traffic to the network and the same services penetration percentage. A simple theoretical approach is taken, enabling the calculation of the maximum cell radius in a single user scenario. Comparing HSPA+ with Mobile WiMAX for the single user model, one can conclude that, for all the environments considered, it is observed that, both for DL and UL, the cell radius decreases with the increase of the throughput, because higher throughputs require higher SR values, which leads to a decrease of the path loss and a reduction of cell radius. For a pedestrian environment, regarding DL in HSPA+, the cell radius varies from 1.34 km, for 6.0 Mbps, to 0.72 km, for 17.0 Mbps, which represents a decrease of 46%. In Mobile WiMAX, the variation observed is not so noticeable, being from 0.27 to 0.16 km for the same interval of throughputs, establishing a reduction of 41%. Relating UL, in a pedestrian environment, the interval of throughputs considered is between 3.5 and 7.6 Mbps. In HSPA+, the radius for 3.5 Mbps is 0.28 km and the lowest radius achieved is 0.17 km. In Mobile WiMAX, the cell radius varies from 0.17 to near 0.09 km considering the same interval. Compared to DL, the ratio between the radii for two systems is not so notorious in UL: 1.7 for a throughput of 3.5 Mbps and 1.8 for the upper limit of the interval. Comparing HSPA+ and Mobile WiMAX in the multiple users scenario for DL, and considering the default values, it is observed that the HSPA+ system covers a large number of users than Mobile WiMAX presenting a higher average network radius. The average network throughput, for HSPA+, is 8.85 Mbps and, for Mobile WiMAX, is 3.26 Mbps. Mobile WiMAX has an average ratio of served users 4% higher than the HSPA+ but its average satisfaction grade is lower and the served services profile shows that the most demanding services, such as FTP, Email and Web, have a lower penetration. Since, in a certain instant, the trade-off of covered and served users is more advantageous for HSPA+, this system can serve 258 000 users in a hour, corresponding to more 137 000 users than the ones served by Mobile WiMAX. The users served in HSPA+, in an hour, are associated to a total traffic of 450 GB/h, corresponding to the triple of the traffic generated by the Mobile WiMAX users in an hour. Comparing HSPA+ and Mobile WiMAX in the multiple users scenario for UL, one can notice that the number of users covered are lower than the DL situation, which introduces a strongly dependence on the type of service that is performed by the users served and on its distribution. Since there are more users covered in HSPA+, explained by its higher average network radius, the average network throughput, for the default scenario, is 1.90 Mbps while, for Mobile WiMAX the value is around 1.08 Mbps, representing a decrease of 43%. Mobile WiMAX, besides serving 28% of the covered users, more 5% than HSPA+, serve them with a lower satisfaction grade when compared to HSPA+. One should further refer that the distribution of served traffic in Mobile WiMAX contemplates less users performing Web, FTP and Email that are the most demanding services. In what regards the number of users per hour, one can refer that HSPA+ serves 45 800 users, more 13 800 than Mobile WiMAX. The total network traffic obtained for HSPA+ is 34GB/h, while for Mobile WiMAX the parameter assumes the value of 23GB/h. REFERECES [1] Holma,H. and Toskala,A., WCDMA for UMTS HSPA Evolution and LTE (4 rd Edition), John Wiley & Sons, Chichester, UK, 2007. [2] Cicconetti, C., Lenzini, L., and Mingozzi, E., Quality of Service Support in IEEE 802.16 etworks, University of Pisa, Italy, March/April 2006. [3] Holma, H. and Toskala A., HSDPA/HSUPA for UMTS, John Wiley & Sons, Chichester, UK, 2006. [4] Bergman, J., Ericson, M., Gerstenberger, D., Göransson, B., Peisa, J., Wager, S., HSPA Evolution Boosting the performance of mobile broadband access, Ericsson Review, 2008 (http://www.ericsson.com/ericsson/corpinfo/publications/review/2008_0 1/files/5_HSPA_Evolution.pdf). [5] Peisa, J., Wager, S., Sågfors, M., Torsner, J., Göransson, B., Fulghum, t., Cozzo, C. and Grant, S., High Speed Packet Access Evolution Concept and Technologies, in Proc. of Spring IEEE 65 th Vehicular Technology Conference VTC200, Dublin, Ireland, April 2007. [6] Mobile WiMAX Part I: A Technical Overview and Performance Evaluation, WiMAX Forum, Feb. 2006. [7] http://www.wimaxforum.org/, Sep. 2008. [8] KDDI and WiMAX convergence in the land of the rising sun, WiMAX Forum, Aug. 2006. [9] Costa,P. and Ladeira,D., Planning of UMTS Cellular etworks for Data Services Based on HSDPA (in Portuguese), Graduation Thesis, Instituto Superior Técnico, Lisboa, Portugal, June 2006. [10] Damasso,E. and Correia,L.M., Digital Mobile Radio Towards Future Generation, COST 231 Final Report, 1999 (http:/www.lx.it.pt/cost231/). [11] Lopes,J. Performance of UMTS/HSDPA/HSUPA at the cellular level, M.Sc. Thesis, Instituto Superior Técnico, Lisbon, Portugal, Mar. 2008. [12] Salvado,L., UMTS/HSDPA Comparison with WiMAX/IEEE802.16e in Mobility Scenarios, M.Sc. Thesis, IST-TUL, Lisbon, Portugal, Mar. 2008. [13] Kuipers,M., and Correia, L.M., "Modelling the Relative MIMO Gain", in Proc. of PIMRC 08 - IEEE Personal, Indoor and Mobile Radio Communications, Cannes, France, Sep. 2008, in press. [14] Preguiça,R., Comparison between UMTS/HSPA+ and WiMAX/IEEE802.16e in Mobility Scenarios, M.Sc. Thesis, IST-TUL, Lisbon, Portugal, Sep. 2008. [15] uaymi,l., WiMAX Technology for Broadband Wireless Access, John Wiley, UK, 2007.