The Fourth Generation ( 4G ) engineering campaigners is foreseen most likely to be between Long Term Evolution Advanced ( LTE-Advanced ) proposed by the Third Generation Partnership Project ( 3GPP ) and Mobile WiMAX utilizing 802.16m standardised by the Institute of Electrical and Electronics Engineers ( IEEE ) . Distinguish the proficient differences between these two engineerings and give your sentiment on the scenario and deployment of 4G in the close hereafter.
Significant Technical Differences
1. LTE and WiMaX employ the extraneous frequence division multiple entree ( OFDMA ) in the downlink. But WiMax optimizes for highest channel managing by developing all the information in a broad channel. LTE, in contrast, arranges the available spectrum into smaller parts. WiMax pays a charge for high channel use, nevertheless, because developing that much information might affect a 1,000-point fast Fourier transform. LTE can obtain by with a 16-point FFT. This interprets into higher power ingestion, because it 's complicated to plan fixed-function WiMax hardware that is besides resourceful in LTE designs.
2. LTE applies single-carrier frequence division multiple entree ( SC-FDMA ) [ 11 ] for uplink signaling, whilst WiMax sticks on OFDMA.
3. Even though both the IEEE 802.13e criterion and the germinating LTE criterion hold up frequency division duplexing ( FDD ) and clip division duplexing ( TDD ) , WiMax applications are chiefly TDD. LTE seems to be traveling in the FDD way because it is right full-duplex operation: Adjacent channels are applied for uplink and downlink. LTE can therefore estimation a better spec for downlink informations rates, though at a cost of puting really terrible latency conditions for frontward error rectification. The chief thing is that the WiMax wireless is much unsophisticated.
At the terminal of 2007, the overall nomadic users were 3 billion, with GSM based users to raise over 2 billion. Some research studies are anticipating that the WiMAX will viably be implemented by 2009 and the LTE ( Long Term Evolution ) by 2015. Nevertheless, the criterions struggle towards the 4G launch is a major concern. ITU and IEEE are trying to procure a smooth transition into the new engineering. ( Figure 1 )
Figure 1: Smooth transition into the new engineering
There are assorted methods that can be used to increase user and system capacity such as by utilizing new multiplexing strategy with enhanced transition strategies. Tabulate and sum up some of import characteristics related to the multiplexing and transition techniques for parallel system ( e.g. ETACS, AMPS ) and digital ( e.g. GSM, GPRS, EDGE, HSPA, LTE, WiMAX ) system. Among them are FDMA, TDMA, CDMA, SDMA, etc. for multiplexing and FM, GMSK, 8-PSK, QPSK, OFDM, MIMO, Adaptive Modulation and Adaptive Modulation and Coding ( AMC ) .
Frequency Division Multiple Access ( FDMA )
Frequency Modulation ( FM )
Frequency Division Multiple Access ( FDMA )
Frequency Moduation ( FM )
Time Division Multiple Access ( TDMA )
Gaussian Minimum Shift Keying ( GMSK )
Time Division Multiple Access ( TDMA )
Gaussian minimum-shift keying ( GMSK )
Time Division Multiple Access ( TDMA )
8 Phase Shift Keying ( 8PSK )
Code Division Mutiple Access ( CDMA )
Multiple Input Multiple Output ( MIMO )
Orthogonal Frequency Division Multiple Access ( OFDMA )
Orthogonal Frequency Division Multiple Access ( OFDMA )
Table 1: Multiplexing and transition technique for parallel and digital system
The public cellular service operator in Malaysia are subjected to compulsory criterions for Quality of Service ( QoS ) or Grade of Service ( GOS ) by Malayan Communication and Multimedia Commission ( MCMC ) . List assorted parametric quantities and strategies used for supplying QoS/GOS in cellular web and discourse their advantages/disadvantages to the endorsers and operators. How can QoS purveying be managed in the hereafter 4G cellular web?
There are difference strategies of QoS in cellular netwoks:
1.0 Fault Tolerant Dynamic Channel Allocation Scheme [ 1 ]
In this strategy the channels are assigned dynamically based on demand and hence increase the channel use every bit good as the quality of service ( QoS ) . The channel allotment strategies are unified and distributed. In a incorporate attack, the cardinal accountant is in charge for channel allotment and the it will direct petition to the accountant while in distributed attack, a Mobile Service Station ( MSS ) is exist in each cell which handles the channel allotment for that peculiar cell. Distributed attack is more scalable and trusty [ 1 ] . Therefore, algorithm is used in this attack.
Figure 1: A Model of Wireless Communication Networks [ 1 ]
Figure 1 shows a wireless communicating theoretical account. Many cells consist Mobile Hosts ( MH ) and a Mobile Service Station ( MSS ) . Each cell is connected to a fixed web. Each MH when it wants to pass on with another Mobile host has to bespeak a channel from MSS for communicating [ 3 ] .In communicating, there are communicating channel and command channel [ 3 ] . A communicating between a MH and a MSS is supported by communicating channel while control channel is employed for directing control messages like MH bespeaking the MSS [ 3 ] in order to put a communicating channel. The channels are assigned by MSS to the MH to see if there is co-channel intervention occurs. A channel for communicating is allocated to the MH if the co-channel intervention does non be.
There two different attacks for necessitating channels. In Centralized attack, Mobile Switching Center ( MSC ) will be used to supply channels for each MH if MH asked for a channel from the cardinal accountant. Hence, the MSC will fix for channel allotment in status that no co-channel intervention exists. In this attack, the MSC might go a constriction in the web [ 3 ] and the whole web will be affected if the MSC experiences interrupt down. This is the drawbacks of the Centralized attack. Hence this attack is non scalable and robust [ 3 ] .
There is no cardinal accountant and each cell has its ain MSS in the Distributed attack [ 3 ] .The neighbours of a cell will have an update about channel use by the cell and notifies them when to discontinue the channel so that others can utilize it. A cell can utilize a channel right after acquiring a answer from its full neighbours informing the cell that the channel is ready to be used.
1.1 System Model [ 3 ]
Channelss are assigned dynamically and non assigned in progress to any cells. A bunch theoretical account is employed where three cells are used with each cell has six neighbours. If a cell uses a channel, its neighbour can non utilize the same channel in order to avoid co-channel intervention. If the cell does non hold any channel, it can borrow a channel with a status that the cell 's neighbours satisfied its petition and besides guarantee that co-channel intervention does non be. There are two types of operation manner which are update manners and hunt manner [ 3 ] . A presentment of a cell about its channel use information to all its neighbours is known as update manner. A cell is able to direct an update about its position to its full neighbours by utilizing this manner. In add-on, a cell can direct a petition message to its neighbour if it wants to borrow a channel and this type of operation is called hunt manner.
1.2 Distributed Channel Allocation Algorithm [ 3 ]
In this theoretical account, three cell bunch theoretical account and each cell has six neighbours and it has a alone neighbour Idaho ordered from one to six [ 3 ] . Channelss are non pre-assigned to any cell. The channel with last frequence has the least order and the channel with highest frequence has the highest order [ 3 ] . A cell Ci selects a channel with the highest order to back up a call if it is available [ 3 ] .
Figure 2: Cell Cluster Model to Illustrate Distributed Channel Allocation [ 3 ]
In figure 2 each cell is numbered from 1 to 6 and we are traveling to utilize cell Ci to bespeak a peculiar cell. When Ci ask for a channel to utilize, it is in hunt manner and it 's called a borrower [ 3 ] . It sends a broadcast message to all its neighbours for the channel and sets a timer and remains till the timer times out. When a cell is in borrower manner it ignores to any question from any other cell inquiring for channels. This is because the borrower itself is in seek for channels and so it 's non traveling to be of any aid to other channels which are bespeaking. This strategy is good in the manner that it avoids unneeded congestion in the web [ 3 ] . Now after the timer times out, the cell Ci will borrow a channel based on the answers which it got from its neighbours [ 3 ] ..
To verify that this algorithm works lets assume that the cell Ci has got answers merely from 2 neighbours, 1 and 4 and there is a channel R which is assigned to both the cells 1 and 4. In this instance the cell Ci can borrow the channel R even though other cells ( 2,3,5,6 ) have non responded other than cells 1 and 4 [ 3 ] .. The ground is that since channel R is assigned to cells 1 and 4, it can non be assigned to the neighbours of cells 1 and 4 ( cells 2, 6, 3 and 5 ) due to co - channel intervention [ 3 ] .. Thus channel Ci can borrow the channel with the responds it got from merely two channels. This confirms that this algorithm is fault tolerant [ 3 ] .
As a consequence the above algorithm which we saw was fault tolerant as it need non wait for [ 3 ] responds from all the channels. This besides indicates that the algorithm is more scalable. It employs distributed channel allotment strategy in which channels are allocated dynamically based on petition. This algorithm besides lets reuse of channels. This implies that a loaner can impart a channel to two or more cells at the same time offered that no co-channel intervention occurs [ 3 ] .
2.0 Call Admission Control ( CAC ) Scheme
In the CAC algorithm new call reaching rates are estimated continuously and if they are higher than a preset degree some calls are blocked irrespective of whether a channel is available or non [ 3 ] .. The end of this strategy is to retain the new call reaching rate lesser than a preset degree. In this strategy a comparing is done with the bing two strategies viz. prerequest strategy and the guard channel strategy and assorted benefits and drawbacks are given for the two strategies and so a CAC algorithm is developed which offers a better QoS than the bing two strategies. The two prosodies used for QoS in this algorithm are Forced Termination Probability ( FTP ) which is named as the ratio of the figure of calls which are forced to end because of failed handoff to the figure of calls that successfully penetrated the web. Another metric is the Successful Call Completion Rate ( SCCR ) which is named as the figure of calls which are finished successfully in a unit clip by each cell [ 3 ] . So lower FTP and higher SCCR is what ideal algorithms will seek to acquire and this algorithm achieves that.
2.1 Channel Prioritization Schemes
In the Guard Channel Scheme several channels are entirely stored for the handoff calls and these channels are called guard channels. A certain figure of channels say G out of C channels are entirely stored for handoff calls of the profiled users. The staying channels are divided for all types of calls. These calls include new calls, handoff calls of profiled users and handoff calls of non profiled users. This is an illustration of inactive allotment of channels.
In the channel prerequest strategy the channels are ask for beforehand before the handoff occurs. The information about the mobility forms of the profiled users is in the Home Location Register ( HLR ) and using this information so that the handoff activities of the profiled users can be predicted. The prerequest channels are inquiring the neighboring cell for a certain sum of clip called as the reserve period. By lifting the reserve period, the opportunities of forced expiration can be significantly decreased.
2.2 Call Admission Algorithm ( CAC )
Figure 3: Flow Chart for CAC Algorithm [ 3 ]
In the CAC algorithm the equal burden is calculated based on simulation results and this value is used for rating intent. The estimated burden is besides calculated and it is verified with the acceptable burden. If the estimated burden is lower than or equal to the satisfactory burden, so efforts are made to delegate channels for all the entrance calls. If the estimated burden is higher than the satisfactory burden so merely a fraction of the entrance calls will be assigned channels and the staying fraction of the calls will be removed even if there are available channels. This is called pre-blocking of channels and this strategy develops the FTP and SCCR of the profiled users.
3.0 QoS based on Mobility Prediction Techniques [ 4 ]
Mobile anticipation techniques are used to happen the way or the flight of a nomadic node and it is reserved in a database from clip to clip. This technique helps in hive awaying resources for MH before a manus off occurs so prioritizing resources takes topographic point for a node before its manus off and therefore this reduces the call barricading rate at manus offs. However the new call entree rate is diminished as more resources are stored for manus off calls. Forced expiration can be decreased by increasing the figure of new call blocking chance. But this is non really resourceful use of the wireless resources. By utilizing nomadic anticipation methods, we can cognize in progress when a handoff will take topographic point and so dynamic allotment of resources for the handoff can be done. This makes certain that the new call blocking chance is non raised so much to maintain resources for the manus off calls. There are legion nomadic anticipation techniques which have been utilized in the yesteryear which includes GPS positioning techniques in which every MH is integrated with a GPS receiving system so that the way of the MH can be traced.
3.1 Road Topology based Mobile Prediction Techniques [ 4 ]
This technique is based on the fact that MH 's in vehicles will come across the most frequent manus offs and so analyzing their features would verify to be more good. Since the vehicles travel on the route, the route topology is considered and is used in the anticipation algorithm. In this strategy the base station will make the Mobile anticipation based on the route topology information it has. Since the base station has more storage capacity and resources than the MH, it is used for better preciseness.
Figure 4: Road Topology Information for Mobility Prediction [ 4 ]
In this technique there are some base Stationss, which are updated with the MH 's most recent place at standard interval of clip. Each base station will continue a database which includes information about the route topology. As shown in figure 5 the route which consists of decompression sicknesss is busted into many piecewise additive line subdivisions and the co-ordinates for these line subdivisions are stored individually. The database has information such as mean clip to pass through a section, neighbouring sections at each junction and the chance of the MH to make a manus off and travel to a following adjacent subdivision. The database is restructured sporadically and at every blink of an eye the information about the location of the MH is obtained. Sections which have already had manus offs are referred to as handoff executable sections. Using this theoretical account, precise anticipation is done, which is practical in prioritising resources for the handoff of an MH.
4.0 Dynamic Allocation Scheme utilizing Renegotiation [ 5 ]
In a Dynamic Allocation strategy utilizing Renegotiation, the unemployed resources of the web are searched and they are allocated to services which got a smaller bandwidth at the clip of entree when they really wanted more. In other words, renegotiation of the bandwidth is done for a lesser precedence service when the medium is free, therefore lifting the full bandwidth of the lower precedence services. The strategy on the other manus besides keeps the bandwidth of the higher precedence beginnings.
4.1 Different Service Classes
Conversational and cyclosis categories are correlated with existent clip traffic and are badly delay sensitive. Examples of these types of services are video telephone, telnet, voice and picture. In contrast, Interactive and background processs are less delay sensitive and they comprise applications like FTP, WWW, electronic mail and intelligence. Since they are less sensitive to detain both these categories give better mistake rates via channel coding techniques. The disagreement between the interactive and the background services are that synergistic services are largely used by synergistic applications like synergistic electronic mail. Background categories are used for background intents which include background browse and background electronic mails.
4.2 Renegotiation Scheme [ 5 ]
In this strategy the colloquial categories are given the highest precedence and they are priority 1 category. The streaming category is besides set high precedence and it belongs to priority 2 categories. Now these precedence 1 and precedence 2 categories will be admitted merely if there are adequate resources ( bandwidth ) to carry through their demands. If non their petitions wo n't be acknowledged. The synergistic service is given the lowest precedence and it is 3. So the demands from these categories are admitted even if the webs have a smaller bandwidth than what they had required. The benefit of the Renegotiation strategy when compared to the CAC strategy is that in the CAC strategy when a bandwidth is allocated to priority 1 and 2 they can non be relocated to a lower precedence category even after the higher precedence category leaves the web. In renegotiation strategy a precedence 3 application can utilize more bandwidth that what was assigned for it. This is made possible because any unemployed resources by the higher precedence categories can be relocated to this category. On the other manus when a high precedence category arrives once more it will non be blocked if the system has low resources. At that clip the bandwidth given to a lower precedence category will be taken back and will be allocated to the high precedence category. Consequently the higher precedence category is non harmed in any manner.
4.3 Renegotiation by Flow Termination
The renegotiation by flow expiration is a agency by which more bandwidth is allocated for a low precedence flow when a high precedence flow terminals or when there are more resources available in the web [ 5 ] .
Figure 5: Behavior of Two Flows Without ( a ) and With ( B ) Renegotiation [ 5 ]
In figure 5 behaviour of two different flows are shown without and with renegotiation. In instance ( a ) without renegotiation the bandwidths of A and B are shown. Even after the expiration of flow A the bandwidth of B remains the same. In instance ( B ) after the expiration of flow A the bandwidth of flow B is increased due to the handiness of resources [ 5 ] .
The Very Small Aperture Terminal, VSAT service is going more popular in Malaysia. Obtain information on VSAT service operator in Malaysia including illustrations of application, web topology, user equipments, lease process and services offered and their informations rate. How can a VSAT system accommodate endorser that need higher information rate services.
VSAT is an ideal orbiter web that offers communications support for a broad scope of applications [ 10 ] :
Fiscal Management [ 10 ]
Data processing [ 10 ]
Reservation System [ 10 ]
Telemetry & A ; Data Collection [ 10 ]
News Wire Services [ 10 ]
Private-Line Voice [ 10 ]
Virtual Private Networks [ 10 ]
Distance Education [ 10 ]
High Speed Internet Access [ 10 ]
The VSAT system has two types of topologies: Star Topology and Mesh Topology
1.0 Star Topology
The star topology is the conventional VSAT web topology. The distant terminus is connected to the hub for communicating. It suited to used this topology for informations aggregation or broadcast medium. The hub station ( dual hop ) is used to pass on between the remote and this makes star topology impractical to offer address services between the terminuss because clip hold in the hub station ( 500 MS ) is high. The digital bearers provide connexion on the infinite section in both waies, which organized with a assortment of entree strategies. The entree techniques used in a star web can be Frequency Division Multiple Access ( FDMA ) [ 9 ] , Time Division Multiple Access ( TDMA ) [ 9 ] , and Code Division Multiple Access ( CDMA ) , but TDMA is the most common.
2.0 Mesh Topology
In mesh topology, there is direct communicating between the distant VSAT terminuss. This direct communicating reduces the clip hold. The signaling processor is placed in the cardinal node, therefore this internal signaling is utilizing leading topology and this is frequently referred to as the demand assignment multiple entree ( DAMA ) . While in a mesh web, it is typically for Frequency Division Multiple Access ( FDMA ) .
Figure 1: VSAT system topologies: star topology and mesh topology. Mesh topology offers direct connectivity between the distant VSAT terminuss [ 6 ]
End User Equipment for satellite Internet entree [ 12 ]
The terminal user equipment consists of the VSAT dish, BUC LNB and the Modem. Depending on where the equipment is placed, they are classified as indoor or out-of-door [ 12 ] .
1.0 The indoor unit [ 12 ]
The IDU is usually a individual box satellite Internet modem which is linked to the client 's computing machine equipment.
1.1 Satellite Modem
A orbiter modem or sat modem is used to put up informations transportations utilizing a communications orbiter as a relay [ 12 ] . The VSAT Systems Indoor Unit ( IDU ) modem has onboard TCP optimisation and QoS ( Quality of Service ) capablenesss, router and DNS. The unit is centrally controlled from a Network Operations Center ( NOC ) [ 12 ] .
The IDU is compatible with Ku and C set service every bit good as Ka set service when it becomes available [ 12 ] .
2.0 The out-of-door unit [ 12 ]
2.1 VSAT Satellite dish
The orbiter dish which is in parabolic form is mounted on the roof. It receives the Ku set RF parallel signals from the geostationary orbiter 23,000 stat mis in the sky and passes it on to the modem. The dish sizes range between.96m to 2.8m. [ 12 ]
VSAT webs in general operate at one of three frequences: C set, Ku set, or Ka set. C set operation needs a larger satellite dish due to its lesser frequence ; nevertheless, it suffers less from rain fading. Ku set dishes are smaller in size and more vulnerable to rain-fade than C set dishes. On the other manus, Ku set dishes work all right even during rain fade scenarios if the modems are set with power hiking capablenesss. Ka-band-based webs are able to utilize even smaller dish sizes, nevertheless, the job of rain fading is exaggerated farther at the higher frequence operations such as Ka. [ 12 ]
Larger dishes provide for better response in distant countries and support much higher bandwidth service programs. The dishes can be stationary, nomadic or portable.
2.2 Block up Converter [ 12 ]
Block up convertor ( BUC ) is employed for the uplink of satellite signals. It works by exchanging a 'block ' ( set ) of frequences from a lower frequence to a higher frequence. As the distances to be traveled by the signal for transmittal are enormous, higher frequences are used as they suffer less fading. BUCs convert the L set to a Ku set and a C set to a Ka set [ 12 ] .
For most applications, BUCs have a evaluation between 3-6 Watts. For other high powered applications, BUCs with larger evaluations are available [ 6 ] .
2.3 Low Noise Block Converters ( LNB )
BUCs are by and large used in concurrence with Low Noise Block Converters ( LNB ) . The BUCs make up the 'transmitting ' subdivision of the equipment whereas LNBs are down-converters, the receive subdivision of the equipment. The receive signal demands to be down converted because Ku set signals received from the orbiter are high frequence signals which suffer greater fading while go throughing through overseas telegrams used for indoor transmittal. [ 12 ]
VSAT Services [ 9 ]
i. Synergistic existent clip application [ 9 ] :
- Point of Sale/retail/Banking ( eg. ATM ) [ 9 ]
- Corporate informations [ 9 ]
two. Telephony [ 9 ]
- Rural: single endorsers [ 9 ]
- Corporate Telephony [ 9 ]
three. Intranet, Internet and IP substructure [ 9 ]
- Multimedia bringing ( eg. picture streaming ) [ 9 ]
- Interactive distance learning/ developing [ 9 ]
four. Direct-to-home [ 9 ]
Broadband Internet entree for consumers and concerns [ 9 ]
VSAT informations rates
The list of informations rates ( in Kbps ) is as below ;
A A 1. 1.2 up to 56
A A A A 6. 512
A A 2. 64
A A A A 7. 768
A A 3. 128
A A A A 8. 1024
A A 4. 256
A A A A 9. 1536
A A 5. 384
A A 10. 2048
How can a VSAT system accommodate endorser that need higher information rate services.
VSAT webs give a manner to put up a switched point to indicate informations web that can hold the capableness for high informations rates of up to 2Mb/s. Connections are set up straight between distant terminuss normally on a call by call footing. These webs are by and large configured to run without a big cardinal Earth station and transport a mix of informations traffic and telephone traffic or merely informations traffic.
Direct Broadcasting Satellite, DBS service such as ASTRO is going more popular. Investigate and research the multiplexing method each Television channels before the channels can be distributed and shown to viewer. How can ASTRO work out the job of signal damage and debasement due to heavy rain, and intervention from WiMAX operators?
In digital telecasting and wireless system, some variable bit-rate informations watercourses are multiplexed together to a fixed bitrate conveyance watercourse by agencies of statistical multiplexing. This makes it possible to reassign several pictures and audio channels at the same time over the same frequence channel, together with assorted services [ 6 ] .
In the digital telecasting systems, this may affect several standard definition telecasting ( SDTV ) programmes ( peculiarly on DVB-T, DVB-S2, ISDB and ATSC-C ) , or one HDTV, likely with a individual SDTV comrade channel over one 6 to 8A MHz-wide Television channel [ 6 ] . The device that achieves this is called a statistical multiplexer. In some of these systems, the multiplexing consequences in an MPEG conveyance watercourse. The newer DVB criterions DVB-S2 and DVB-T2 have the ability to transport several HDTV channels in one multiplex. Even the original DVB criterions can transport more HDTV channels in a multiplex if the most advanced MPEG-4 compactions hardware is used.
On communications orbiters which carry broadcast telecasting and wireless web, this is known as multiple channels per bearer or MCPC [ 6 ] . Where multiplexing is non realistic ( such as where there are different beginnings utilizing a individual transponder ) , individual channel per bearer manner is employed.
Signal multiplexing of satellite Television and wireless channels is normally carried out in a cardinal signal playout and uplink Centre, such as Astro in Malaysia, which offers playout, digital archiving, encoding, and satellite uplinks, every bit good as multiplexing, for some of digital Television and wireless channels.
How can ASTRO work out the job of signal damage and debasement due to heavy rain, and intervention from WiMAX operators
The direct-to-home ( DTH ) , is broadcast as high-octane Ku-band transmittals utilizing the transponders of the MEASAT orbiter system. Reception of the service signals utilizes a fixed 60-cm diameter dish aerial.
Ku-band signals can be influenced by rain fading ( rain slice ) , doing it vulnerable to frequent outages in heavy rainfall countries such as Malaysia, the operators of Astro have utilized a bespoke system to increase power of the orbiter bringing system to get the better of this job. The service handiness of 99.7 % , nevertheless, is still a issue of much argument by endorsers.