Integration of Ad-Hoc Networks with Infrastructured ... - Semantic Scholar

Integration of Ad-Hoc Networks with Infrastructured Systems for Multicast Services Provisioning Silverio Carlo Spinella, Giuseppe Araniti, Antonio Iera, Antonella Molinaro ARTS Laboratory – Department DIMET University Mediterranea of Reggio Calabria Loc. Feo di Vito, 89100 Reggio Calabria - ITALY Email: {silverio.spinella, araniti, antonio.iera, antonella.molinaro}@unirc.it

Abstract— Focus of this paper is on an integration framework between UMTS (Universal Mobile Telecommunications System) and Mobile Ad-hoc NETworks (MANET), specifically designed to increase the effectiveness of cellular networks in supporting multicast transmissions. The aim is to overcome the scalability constrains of cellular system by enriching it through multi-hop communications. To the purpose of reducing the adverse impact of multicast transmission in the wireless cellular environment and to improve the system scalability, in this paper we propose a Radio Resource Management (RRM) policy based on a MBMS/MANET integrated architecture. The proposed solution has been successfully tested through a comprehensive simulation campaign. Obtained results make us confident that a welldesigned integration is a promising approach to overcome the UMTS (and beyond UMTS networks, as well) inadequacy in supporting multicast services efficiently. Keywords: MANET, MBMS, Multicast, Scalability, UMTS.

I.

INTRODUCTION

Nowadays, the introduction of efficient multicast transmission policies has been proven to enhance the overall system scalability in wireless environments. Fervent research activities have been conducted by UMTS standardization group to specify the Multimedia Broadcast/Multicast Service (MBMS) [1] protocols that will allow to support group oriented multimedia services in the UMTS network [2]. In the view of containing costs, the first approach followed by the UMTS standardization group consisted of adapting the existing unicast protocols and network infrastructures to support multicast traffic. In particular, in the Core Network (CN) new functional blocks have been identified to support multicast IP protocol. Differently, within the UTRAN (UMTS Terrestrial Radio Access Network), multicast traffic must share radio resources with the unicast traffic, because no multicast channel has been defined. It clearly emerges that the highlighted choices imply significant results in term of scalability in the CN, while, on the UTRAN side, the situation is far from a solution. Just to give an example, it is foreseen that the limited radio resource capacity would be saturated if only 40% of 3G customers utilize video streaming and/or TV services more than eight minutes per day [3].

With our research we try to contribute to the issue of radio access network scalability improvement, by taking advantages of the integration among different networks. Indeed, networks integration represents an interesting way to support multimedia services in terrestrial cellular networks as it allows to increase the efficiency of the whole system in terms of coverage area, resources capacity, and number of simultaneously active users. It is the authors’ opinion that MBMS/MANET integration is a valid approach for multicast service delivery, which offers an effective solutions to the MBMS issues raised. Thus, objective of this paper is to evaluate a possible MBMS/MANET architecture and to define a feasible RRM policy to manage multicast traffic delivery in presence of multiple MBMS sessions. With reference to integrated cellular/MANET scenarios, interesting studies have been conducted so far, aiming at increasing the total throughput, the coverage area, and the amount of available radio resources in cellular networks [4-6]. Many of the cited researches focus on Point-to-Point (PtP) traffic, and, as a consequence, are not straightforwardly applicable to group oriented transmissions. Just a few recent proposals concern Point-to-Multipoint (PtM) transmission protocols [7, 8]. A very interesting performance analysis of multicast streaming in heterogeneous MBMS/MANET networks is reported in [8]. Compared to the state-of-the-art, our paper is different in that we conduct our researches by considering: (i) the possibility of multiple multicast sessions within the same coverage area; (ii) the analysis of UMTS performance in terms of multicast and overall traffic grade of service; (iii) a realistic MANET coverage area according to the most recent WiFi technologies integrated into mobile phones available on the market. In the remaining part of this paper, we will demonstrate how the envisioned integrated solution can significantly increase the scalability of the system, with a consequent improvement of the overall GoS (Grade of Service). Section 2 gives a brief overview of the MBMS architecture. Section 3 introduces our MBMS/MANET architecture and RRM scheme. The main results of a simulation campaign carried out to test the robustness of the proposed approach are the focus of Section 4. Conclusive remarks are given in Section 5.

II.

UMTS-MBMS FEATURES

MBMS is the multicast technology developed by the 3rd Generation Partnership Project (3GPP) to be made available into the UMTS architecture. MBMS is a downlink Point-toMultipoint protocol thought for the delivery of multicast and broadcast streams generated by a single source. The system architecture to offer MBMS services is shown in Figure 1.

Figure 1: The MBMS architecture [1]

The elements that belong to such architecture are the following: SGSN (Serving GPRS Support Node) carries out user individual service control functions and gathers together all individual users of the same MBMS service into a single MBMS group. The main advantage of Multicast and Broadcast applications is that data is sent once each link. The SGSN indeed maintains a single connection with the source of the MBMS data. GGSN (Gateway GPRS Support Node) terminates the MBMS GTP (GPRS Tunneling Protocol) tunnels from the SGSN and links these tunnels via IP multicast with the MBMS data source. BM-SC (Broadcast-Multicast Service Center) is an MBMS data source. MBMS data may be scheduled in the BM-SC, e.g. for transmission to the user every hour. It offers interfaces where the content provider can request data delivery to users. The Gmb (or Gi) reference point between BM-SC and GGSN enables the BM-SC to exchange MBMS service control information with the GGSN. UTRAN (UMTS Terrestrial Radio Access Network), including Node-B and Radio Network Controller (RNC), which is in charge of the MBMS service distribution across the multicast service area. It also establishes PtP and PtM connections over the air interface, identifies MBMS users within a cell, chooses the most suitable (PtP or PtM) channel type, supports both intra-RNC/NodeB and inter-RNC/NodeB mobility, and transmits MBMS service announcements and paging information. UE (User Equipment), which receives data according to MBMS protocol. MBMS services can utilize over the radio interface both Common (Forward Access Channel, FACH) and Dedicated (Dedicated Channel, DCH) channels, as well as a Shared transport channel (High Speed Downlink Shared Channel, HSDSCH) [9, 10]. The choice of allocating to a group of users either one PtM channel or several PtP channels plays a key

role: if one chooses to allocate a PtM channel, then one single transport channel is used, else several PtP transport channels are used, one per user [10]. The FACH is a broadcast common downlink transport channel that carries control information to terminals known to be located in the given cell. This is used, for example, after a random access message has been received by the base station. It is also possible to transmit packet data on the FACH. It does not use fast power control, and the messages transmitted need to include in band identification information to ensure their correct reception. The only dedicated transport channel is the DCH that carries all the information intended for the given user coming from layers above the physical one, including data for the actual service as well as higher layer control information. The DCH is characterised by features such as fast power control, fast data rate change on a frame-by-frame basis, and the possibility of transmission to a certain part of the cell or sector with varying antenna weights with adaptive antenna systems. The HS-DSCH is the shared transport channel that carries the actual user data with HSDPA that is the downlink transmission technology of the High Speed Packet Access (HSPA) family. Despite the efforts, still the MBMS standard has not completely solved the problems related to its main weakness: the capacity for novel PtM services is provided within the same spectrum used by PtP transmissions, with a consequent prospective decrease in the overall system GoS. In [11] it has been demonstrated that the simultaneous transmission of parallel MBMS sessions further reduces the system performances. This means that in the presence of more than one multicast group the MBMS is not a scalable protocol. A promising way to overcome MBMS intrinsic limitations consists in integrating MANET technologies into UMTS networks, as introduced in this paper. This solution foresees that multi-interface UMTS terminals cooperate in the multihop access to the cellular infrastructure by exploiting their short-range WiFi interface. In so doing, a UMTS terminal will play the role of Anchor Node (AN) and receive the multicast traffic from the UMTS interface (as an example, over a DCH channel); subsequently, it conveys the received packets, across the WiFi interface, to its neighbour terminals within the MANET. This implements a cooperative behaviour between the UMTS/MBMS system and several MANETs with the objective to enhance access capability and reduce costs (user perspective), as well as increase overall capacity, system scalability and cellular system coverage (carrier perspective). III.

THE PROPOSED ARCHITECTURE

A feasible solution to reduce the waste of resources deriving from the allocation of a DCH to each participant of any multicast group is depicted in Figure 2. The Figure shows an UMTS cell coverage area wherein several users are interested in downloading multicast services through the Node B. It can be noticed that, depending on the mutual user reachability, a number of MANETs can be established; for each group the election of either one or more ANs is foreseen. ANs are terminals served by the Node B through DCH channels. They receive the multicast services directly from the cellular network and forward the contents throughout the

MANET. This means that users cooperate with each other to achieve the common goal of enjoying a multicast service at a given quality of service and, at the same time, interaction between the MANET and the cellular network is established to increase the cellular network capacity. The choice to employ a terminal as an AN is taken according to policies that account for different parameters, as described in more details below.

connected to the Old Anchor Node. The cited procedure exploits metrics such as: Signal to Noise Ratio (in the following A); Minimum distance from the Old Anchor Node (in the following B); Mobility level (in the following C); Battery level (in the following D). Similarly to the Cluster Head (CH) election procedure in [12] with reference to a sensor network, we apply an Analytic Hierarchy Process (AHP) [13] to decide the relative weights of an evaluative criteria set according to the aforementioned metrics. The AHP is a theory of measurement through pairwise comparisons and relies on the judgements of experts to derive priority scales. The node with the highest weight will be chosen by the RNC to be the new AN. In our case, the following decreasing priority order is established: D, B, A, and C. For the ANs, more exposed to battery consumption due to their role, economic compensation mechanisms can be thought, such as, for example, the release of credits to use for future exploitations of multicast services. In Figure 3 we show the block diagram of the RRM policy. START

Retrieve UEs Parameters per cell: 1. Number of MBMS sessions 2. Number of UEs per MBMS sessions 3. UE’s distances from Node Bs 4. Radio Bearers of MBMS sessions 5. UE’s Eb/N0

Figure 2: MBMS cooperative scenario

The RRM algorithm proposed in this paper has a threefold objective: (i) to define the access modality to the UMTS/MBMS infrastructure from mobile terminals either directly (by means of DCH channels) or indirectly (multi-hop through the ad-hoc networks terminating to an AN); (ii) to monitor, in pre-established intervals, the power consumed by each MBMS session, to switch from a transport channel to another (more efficient) one; (iii) to continuously monitor network and terminals conditions to the purpose of implementing the right policy for the election and the management of the ANs at an RNC (Radio Network Controller) level. Specifically, when a user terminal requests the access to a given multicast service, it checks in advance whether a FACH or HS-DSCH channel is already active for the same service. Should this be the case, then it joins the multicast group by accessing the aforementioned channel according to the MBMS rules. Otherwise, during a listening phase it searches for a reachable MANET handling a group/subgroup of users receiving the same multicast service. Following the identification of a target MANET, a join procedure is triggered by means of a connect query and the terminal keeps waiting for a reply from the AN. This latter first checks that the acceptance of the new user in the MANET does not cause the trespassing of the threshold (ThrQoS) on either the maximum number of users it is allowed to serve or the maximum number of hops. In this case the new user will become a member of the multicast group/subgroup; while, in case of negative reply, the user requests a DCH channel to the UMTS network. Logically, in the latter case, the new user becomes a potential new AN of a MANET that will support any future request of the same multicast service. In case a novel terminal enters/leaves a MANET, the relevant AN updates its local database and signals the event to the RNC, which updates its global database. In so doing, any time an AN leaves the system (Old Anchor Node), the UMTS network will be able to re-elect a novel AN (New Anchor Node) among the terminals previously

Computation of power levels per cell per MBMS sessions: 1. For DCH 2. For HS-DSCH 3. For FACH 4. For MANET Link

Periodic Check

Retrieve UEs/ANs per MANET Cluster: 1. Battery level 2. Min Distance from Old AN 3. SNR 4. Mobility level

NO

Election/Re-election AN for same multicast service

YES

Select appropriate trasport channel per MBMS session Select AN for same multicast service

PFACH < min (PHS-DSCH, PDCH) Select FACH

Per-node throughput < ThrQoS && PDCH < min FACH (PHS-DSCH, PFACH) Multiplexing Select PFACH, TOTAL DCHs (New AN) Compute total power (Ptotal) for MBMS sessions for cell

Per-node throughput ≥ ThrQoS

Assign RBs to MBMS sessions

YES

NO Ptotal < PMBMS

PHS-DSCH < min (PDCH, PFACH) Select HS-DSCH

1. Reduce Rb (FCFS) 2. Pause session (FCFS) 3. Drop session (FCFS) 4. Reduce ThrQoS

Figure 3: Block Diagram of the RRM policy

Like in [14], we consider a power computation phase where, by processing the data received from the BM-SC and RNC, the required power is computed to be allocated for any MBMS session. In the Radio Bearer (Rb) selection, the PDCH (power required for DCHs), the PFACH (power required for FACH) and the PHS-DSCH (power required for HS-DSCH), are compared in order to select the most efficient transmission method for any MBMS session in a cell. Thus, for any MBMS session, the RRM decides which option allows to spare power and, consequently, chooses the corresponding radio bearer for this session. We define Ptotal, the sum of the power assigned to all the active MBMS sessions in each cell. This power will be compared to the maximum available power assigned by the network provider to MBMS sessions in each base station (PMBMS). In Figure 3 our updates are showed with grey blocks.

Compared to [14], we consider two new procedures: (i) AN Selection and (ii) AN Election/Re-election . The former allows to evaluate if a new user can become a member of the multicast group/subgroup managed by an AN. The latter decides if a MBMS user can become a new AN to support users requiring the same multicast service. The user, obviously, starts an AN Selection procedure if neither a common or a shared transport channel is active and cannot be activated for its multicast service. We define a new metric named per-node throughput that will be used by RNC during this procedure. This parameter is defined as the ratio of bit rate received by a multicast group member over the expected bit rate. It, as will be shown in the following, depends either on the maximum number of users in the MANET and on the maximum number of allowed hops. Thus, it is compared with the ThrQoS: a per-node throughput ≥ ThrQoS means that the new user will join the AN; • a per-node throughput < ThrQoS means that the new user likely will utilize a DCH channel. For the AN Election/Re-election procedure, instead, the UE parameters evaluated at RNC level are the metrics in input to the aforementioned AHP, in order to choose the best AN. If Ptotal < PMBMS, then the suitable transport channel is assigned to the MBMS session. Differently, when Ptotal ≥PMBMS, a session reconfiguration procedure should occur due to the fact that there are not enough radio resources available in the Node B to serve all the MBMS sessions. In [14], three possible reconfiguration events are considered: (i) the reduction of the transmission rate of a MBMS session; (ii) the pause of a MBMS session for a short period of time; (iii) the cancellation of the service. According to the new procedures introduced, a further reconfiguration event should be considered, i.e. the reduction of ThrQoS. In so doing, as we will show in the following, a higher number of users will join the AN. •

IV.

probabilities below the target values of 10%. We assume that 80% of unicast users utilize phone services while the remaining 20% utilizes videophone services, while the multicast traffic is supposed to be video streaming. Objective of our campaign is to evaluate the impact of the proposed architecture on standard MBMS, by highlighting introduced advantages and observed limitations. In particular (refer to Table I) we assume several multicast groups receiving different MBMS streaming services at the same time from the same base station. Obviously, when a single multicast service per Node B is established, the complexity deriving from the integration between MBMS and MANET is not justified. In our scenario, we evaluate the UMTS performance when in the presence of several multicast groups, simultaneously. The standard MBMS RRM policy foresees that the most numerous multicast group is handled by the multiplexed FACH channels and by the HSDSCH channel; while users belonging to other groups served by the same cell have DCH channels allocated.

UMTS Features

Table I. Simulation Assumptions Features Microcell radius Microcell number Channel propagation model Maximum Base station Tx Power Other BS Tx Power User Speed FACHs Tx Power #FACH channels per microcell at 64Kbps HS-DSCH Tx Power #HS-DSCH channels per microcell Coverage radius Multicast Routing Protocol

MANET Features

Propagation Model

SIMULATION RESULTS

A thorough simulation campaign is conducted to demonstrate that the integration between cellular and MANET networks can improve the performance of a Beyond-3G systems, in terms of capacity, coverage area and scalability, while providing access to multicast streaming services. Our RRM algorithm has been implemented in the NS2 (Network Simulator) simulation environment [15]. Results described in this section are obtained with a 95% confidence interval. The main assumptions during the performed test campaigns are available from Table I. For UMTS system we assumed a perfect power control. This allowed us to introduce some simplifications in our system simulator in according to as reported in the standard. A Poisson distributed call inter-arrival time is assumed for both unicast and multicast users. As for the simulations shown in the present paper, the values of the multicast offered traffic (Erlang/cell) depend on the specific simulation objective and vary during the tests; while, the unicast offered traffic is kept unchanged. Indeed, the majority of simulations, performed under different unicast offered traffic values, always show a similar behaviour. This is why, without losing generality, curves we are going to comment refer to the sample value of Unicast Offered Traffic = 50 Erlang/cell at RNC level. Without the presence of multicast traffic, this value guarantees blocking

Multicast Traffic

Data Rate Number of hops Multicast Services (over dedicated/shared/common channels) Frame Size Frame Speed Video Duration Packet Size Packet/second Number of Active Multicast Groups User Geographical Distribution Offered Traffic Unicast Services (over dedicated channels)

Unicast Traffic

Unicast Services (over dedicated channels) User Geographical Distribution Offered Traffic

Values 0.3 Km 16 Okumura-Hata 20 W (43 dBm) 5 W (37 dBm) [0:5] km/h 6,3 W 2 7W 1 [10:100] m ODMRP 2-Ray Ground Reflection 11 Mbps 1,2,3,4 Video Streaming at 64 kbps 400 bytes 20 frame/s 300 s 1200 bytes 6,67 More than 4 Uniform [50:400] Erlang/cell Phone 12,2 kbps Videophone 64 kbps Uniform 50 Erlang/cell

As reported in Table I, we conducted our simulation considering both fixed and mobile users. In particular we consider a user speed varying in the range [0:5] Km/h, in according to UMTS technical specifications. User mobility doesn’t increase the power computation for UMTS system. Nevertheless, a mobility scenario could reduce the MANET performances in term of throughput, connectivity and as a consequence the capacity of the overall system could decrease. In our simulated system NCommon/Shared is the percentage of multicast users (i.e. a percentage of multicast offered traffic) served by the common and shared channels. By varying the

parameter NCommon/Shared, in Figure 4 we show the variation of the overall system call blocking probability. As expected, the overall blocking probability increases with the multicast offered load, while it decreases when the percentage of multicast traffic belonging to the multicast group handled by the FACH and HS-DSCH channels (NCommon/Shared) increases. For instance, by considering 400 Erlang of multicast offered traffic per cell, the total blocking probability ranges from 75% (when NCommon/Shared=10%) to 49% (when NCommon/Shared=40%). Even if a further increase in term of NCommon/Shared provides a reduction of overall blocking probability, obtained results show that standard MBMS procedures are currently inadequate to support multicast traffic for different groups simultaneously. A subsequent step in our simulation campaign is the assessment of the positive impact a wise integration of MBMS and MANET system has on the performance of the resulting multi-hop cellular system in terms of GoS. In Figure 5 the total blocking probability of the system is shown when the MBMSMANET network integration mechanism is enabled during the user access. Curves are sketched when the Wi-Fi radius coverage (WFRadius) varies and for different maximum number of allowed hops (HMax) between AN and multicast MANET receivers. It is worth noting that choosing a given Wi-Fi coverage radius corresponds to define a given level of transmission power of the 802.11 IEEE terminal interfaces. Obviously, a higher transmission power entails both a greater WiFi coverage radius and a greater number of users served by a single AN. In Figure 5 the worst case in terms of blocking probability is considered (from Figure 4, this is 400 Erlang/cell and NCommon/Shared equal to 10%). Figure 5 shows that, when integrating MBMS and MANET, a reduction of the blocking probability is obtained by increasing either WFRadius or HMax. As a consequence, the total blocking probability observed for standard MBMS might be potentially reduced to values below the acceptability threshold of 10% when a multi-hop integrative access is adopted (as an example, for WFRadius>50m and HMax≥3).

This metric allows to perceive the increase in the scalability consequent to the introduction of a multi-hop cooperative access into the integrated cellular/WiFi system. Capacity gain values increase with WFRadius and with HMax. This increasing does not require any cellular infrastructure augmentation, because the additional WiFi access capability is directly provided by the dual-mode mobile terminals. It is worth noting that for a given value of WFRadius and HMax all offered traffic will be served by integrated UMTS/MANET network and, as consequence, the scalability gain will assume constant values.

Figure 5: MBMS/MANET Overall Blocking Probability; NCommon/Shared=10% and Offered Multicast Traffic=400 Erlang/cell

Figure 6: Scalability Gain

Figure 4: UMTS Overall Call Blocking Probability

Figure 6 shows the capacity gain, defined as the ratio of the capacity of the integrated UMTS/MANET with multi-hop cooperative access ( CUMTS / MANET ) over the capacity of the standard UMTS MBMS system (CUMTS): Capacity _ Gain =

CUMTS / MANET CUMTS

The price to pay is in terms of throughput reduction for multicast users, as a consequence of the increase in the maximum number of multicast terminals that access the system through a given AN. The Figure 7, in fact, shows the per-node throughput values for a given multicast MANET receiver when varying the WiFi radius and the maximum number of allowed hops. Per-node throughput has been calculated for each multicast MANET receiver and the mean value has been evaluated. The per-node throughput values decrease with WFRadius and HMax, because the number of users served by a single AN increases and, as consequence, a higher packet collision is experienced. In Figure 7, the dashed line shows a tolerable ThrQoS. Other two interesting parameters to take into account are the delay and jitter. As a consequence, simulation campaigns regarding the mean delay and jitter of multicast traffic when varying WFRadius and HMax has been conducted with the aim to evaluate how the introduction of multi-hop system can affect these parameters. Although both indexes increase with WFRadius and HMax, still the obtained values (not reported for limited paper size) are such as not to adversely

affect the perceived quality of video streaming applications. In fact, obtained delay and jitter values are respectively lower than 5 seconds and 100ms. These values don’t affect the quality of multicast streaming transmission.

we demonstrated that the number of multicast sessions can be increased, without adversely affecting unicast traffic in a cellular MBMS scenario. Furthermore, the trade-off between the maximum capacity and the guaranteed QoS (Quality of Service) allowed to MANET nodes has been evaluated. Obtained results may represent a valid support to the effective system design activity. REFERENCES [1] [2] [3] [4]

Figure 7: Per-node throughput when varying WFRadius and HMax [5]

By summarizing, it can be stated that increasing the number of nodes connected to the same AN increases cellular system capacity and scalability; at the same time, per-node throughput values decrease with WFRadius and HMax, because the increase in the number of users served by a single AN implies a higher packets collision. A wise dimensioning study is thus required to enable the RNC to best choose WFRadius and HMax values (i.e. those allowing, at the same time, system blocking probability and ThrQoS within their relevant acceptability ranges) for any given loading condition. To this aim, evaluation campaigns are also conducted for loading values equal to 100, 200, and 300 Erlang/cell. Table II summarizes the results.

[10]

Table II. Wi-Fi radius ThrQoS 90% and max blocking probability 10%

[11]

Erlang/cell

100

200

300

400

63 ≤ r ≤ rmax 50 ≤ r ≤ rmax 47 ≤ r ≤ rmax 45 ≤ r ≤ rmax

76 ≤ r ≤ rmax 51 ≤ r ≤ rmax 48 ≤ r ≤ 98 47 ≤ r ≤ 97

77 ≤ r ≤ rmax 55 ≤ r ≤ 88 50 ≤ r ≤ 83 48 ≤ r ≤ 78

80 ≤ r ≤ 90 56 ≤ r ≤ 70 50 ≤ r ≤ 60 48 ≤ r ≤ 50

[6] [7] [8] [9]

[12]

HMax 1 2 3 4

For different combinations of traffic load and HMax, the value of the WiFi radius guaranteeing throughput/blocking probability values above/below the acceptability threshold is reported. As a conclusion, the simplest RNC policy could consist in monitoring the offered load, choosing the best combination of Wi-Fi transmission power and number of allowed hops, and in communicating them to the multicast terminals. The introduction of these new features into the RNC requires negligible modifications also in the ODMRP (OnDemand Multicast Routing Protocol) protocol. Specifically, new Signaling and Control Packets shall be introduced to vary the maximum number of allowed hops and to efficiently manage the multicast MANET receivers connected to the Anchor Node. V.

CONCLUSIONS

This paper reported the analysis of a RRM algorithm for a multi-hop scenario in which MANETs interact with a cellular system to reach the common goal of enhancing MBMS services access. Through an exhaustive simulation campaign

[13] [14] [15]

3GPP TS 25.346 V7.0.0 (2006-03): “Introduction of the Multimedia Broadcast/Multicast Service (MBMS) in the Radio Access Network (RAN)”; Stage 2, (Release7). M. Malkowski, et Al. , “Spectrum efficient multicast and asymmetric services in UMTS including performance simulation results“, OVERDRIVE 2004. TR - Mark Heath and Alastair Brydon with Ross Pow (Analysys Research), “Making a Success of Mobile TV and Video: 3G MBMS versus DVB-H, DMB and MediaFLO”, Sep. 2005 Cavalcanti, D., et al.: “Issue in Integrating cellular Networks WLANs, and MANETs: A Futuristic heterogeneous Wireless Network”, IEEE Wireless Communications, Vol. 12, No.3, pp.30-41 (2005). Cho, J. and Haas, Z.J.: On the Throughput Enhancement of the Downstream Channel in Cellular Radio Networks Through Multihop Relaying, IEEE J-SAC, Vol.22, No.7, pp.1206-1219 (2004). A.N. Zadeh, B. Jabbari, R. Pickholtz and B. Vojcic, “Self-organizing packet radio ad hoc networks with overlay (SOPRANO),” IEEE Commun. Mag., vol.40, pp.149 – 157, 2002. Bhatia R., Li Li , Haiyun Luo, Ramjee R., “ICAM: integrated cellular and ad hoc multicast”, Mobile Computing, IEEE Transactions on, NJ, USA, vol. 5, pp.1004-1015, 2006. Mariann Hauge and Øivind Kure: “A Heterogeneous Multihop Wireless Access Network for Multipoint Streaming: A detailed Performance Analysis”, IPSJ Dogital Courier, Vol. 3, pp.332-342 (2007). M. Chuah, Teck Hu, W. Luo, “UMTS Release 99/4 Airlink Enhancement for Supporting MBMS Services”, IEEE - ICC 2004. IST-2001-35125 (OverDRiVE) Deliverable of the project D08, “Spectrum efficient multicast and asymmetric services in UMTS”. G. Araniti, A. Iera, A. Molinaro, "Effective Service Delivery and Group Management in Integrated Terrestrial-HAP Systems for Multicast Communications", WCMC Journal, 2008, DOI: 10.1002/wcm.676. Y. Yin, J. Shi, Y. Li, and P. Zhang, "Cluster head selection using analytical hierarchy process for wireless sensor networks," IEEE 17th PIMRC, Helsinki, Finland, pp.1–5, 2006. T. L. Saaty, Fundamentals of Decision Making and Priority Theory with the Analytic Hierarchy Process, RWS Pubs., 2000. A. Alexiou, C. Bouras, E. Rekkas, “Efficient Delivery of MBMS Multicast Traffic over HSDPA”, IEEE Symposium on Computers and Communications, 2008. The Network Simulator–ns-2, http://www.isi.edu/nsnam/ns/.