Mobile Communications ebook free download Jochen Schiller. Posted on Tuesday, 16 October by Unknown. Mobile Communications ebook free. Mobile Communications, 2nd Edition. Jochen Schiller, Institute of Informatics, Freuie Universitat Berlin. © |Pearson | Available. Share this page. Mobile. Cellular Wireless Networks. Mobile IP - Dynamic Host Configuration Protocol. Jochen Schiller, “Mobile Communications”, 2nd Edition, Pearson Education.
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Jochen H. Schiller. Mobile. Communications. Second Edition ISBN 0 6. The right of Jochen Schiller to be identified as author of this work has been. Mobile Communications By Jochen Schiller – PDF Free Download Mobile Publisher: Addison Wesley; Language: English; ISBN ; ISBN . Mobile Communications 2nd Ed. by Schiller musicmarkup.infoonmanual - Download as PDF Download as PDF, TXT or read online from Scribd Jochen H. Schiller, Freie Universität Berlin, Germany [email protected], musicmarkup.info
Jochen H. The operators have to install new radio access networks, i. The situation is similar for operators using cdmaOne IS technology. However, these operators go for cdma as this system allows them to reuse their already existing infrastructure. Right now, it does not seem that there is a place for a third 3G system. Wireless Transmission 2.
Here the advantage is the low overhead when starting communication: National authorities regulate frequencies in different nations. Interference happens if senders are too close to each other. As soon as matter is in the way waves travel even slower.
A disadvantage of reservation schemes is the latency for data transmission. This wastes time in case of a very lightly loaded medium. Reservation schemes can also guarantee bandwidth.
Interference happens if senders transmit data at the same time. What if station C in figure 3. Compared to classical Aloha the collision probability is lower because the contention period is kept short compared to the contention-free period where transmission takes place.
Countermeasures are tight synchronisation and guard spaces time gap between transmissions.. Interference happens if senders transmit data at the same frequency. Interference happens if senders transmit data using non-orthogonal codes. Before terminals can start transmission they have to reserve the medium.
The receiver will calculate for A: All non-deterministic schemes. This example should just give a rough feeling what the problems are. Noise can obviously affect the signal.. The receiver then receives for A: Both results are negative. For B the result is: The transmitted signal is then: But still the receiver can distinguish between the two signals — our simple example uses perfectly synchronised signals the spread symbols are in phase.
The lower the correlation is. Also implicit reservations can give guarantees after the reservation succeeded. Common features are traditional voice support circuit switched. One possible step towards the support of data transmission is the introduction of packet switched services as known from the Internet.
DECT local coverage.
Instead of time-based billing providers can now bill based on volume however. TETRA regional coverage. Telecommunication systems 4. DECT can support high user densities. ISDN core network. Data transmission happens quite often spontaneous with varying data rates. The systems have different.
UMTS medium coverage. GSM has wide area coverage. Separation of services supports phased introduction of services and separation of concerns: TETRA ad-hoc mode and fast connection setup. GSM wide area coverage. Thus either too much bandwidth is reserved to accommodate the maximum expected data rate or data transmission experiences long delays due to connection setup.
Reflection and attenuation makes the calculation more difficult. Inside the core network only temporary identifiers are used. This separation helps changing phones while keeping personal data: User data is protected in several ways: The SIM contains subscriber related functions and data: Network operators store all user related information in the HLR and all information related to visitors within a certain location area in a VLR.
Specifying all or at least many internal interfaces allows for a larger variety of vendors. Localisation could be terminal assisted: Besides the SIM also the mobile phone itself can store user-related data. PIN etc. Capacities of HLRs is up to some million customers. As long as vendors stay with the standardised interfaces equipment of different vendors can be combined and network operators are not completely dependent from one manufacturer.
Additional user-related data is stored in the VLR responsible for the location area a user is currently in and the HLR of the network operator the user has a contract with.
All signals must arrive synchronised at the base station. If many users move between location areas updates have to take place. For standard scenarios — most users stay most of the time within their location area — the 2-level hierarchy works well. More levels of hierarchy could improve scalability but also raises complexity.
This limitation is not because of too strong attenuation. The number of channels is operator and regulation dependent. New modulation schemes can offer higher capacity.
These routers SGSN. With some tricks the diameter can be doubled. EDGE is an example.. Regulation authorities assign channels to operators. Terminals have to access the base station suing a slotted Aloha scheme for the layer 2 signalling connection. The terminal itself is responsible for precise synchronisation within the cell. HSCSD has the additional problem of requesting.
Base stations assign a time-slot or several time-slots to a terminal for transmission. This is very important in TDM systems as otherwise neighbouring data may be destroyed. During data transmission or voice call no collision can occur.
Terminals listen into the medium. Within each time-slot during transmission a midample further improves synchronisation. Operators design the cell layout. During this connection attempt several terminals may collide and have to repeat the connection attempt. Experiments show that packets in GPRS may experience heavy delays due to channel access delays: These phone numbers are completely independent of the current location of the user. Each time a user changes the location area this change is reflected in the VLR.
If a TCH exists and more signalling is required e. The latter is the most common scenario as national roaming typically involves direct competitors. Prerequisite are roaming agreements between the different operators. This can happen within the same country national roaming or when going to another country international roaming. That is all users should see. After the assignment of time-slots the terminal may access these slots without further collisions.
Channel assignment and release is handled dynamically in GSM systems. Depending on the current load. For GPRS. The system itself needs some additional information. The international identification of users is done with the. Roaming includes changing the network operator. If no traffic ch channel TCH exists. Precise localisation of users is performed during call setup only paging within the location area. These may be occupied. The tuple TMSI. This hides the identity of a user. The location area identity describes the LA of a network operator.
Consists of the mobile country code 3 digits. These are already some examples for identifiers. The mobile station roaming number is a temporarily assigned. During operation within a location area. LAI uniquely identifies a subscriber. GSM provides some more: MS identification like a serial number. Subscriber identification. It consists of a country code 3 digits. The mobile network code together with the mobile subscriber identification number forms the national mobile subscriber identity.
Another reason could be the current load situation: There is not even a QoS guarantee for a voice call — if the next cell is already completely booked the connection will break upon entering this cell.
The base transceiver station identity code identifies base stations 6 bit and consists of a 3 bit network colour code and a 3 bit base transceiver station colour code.
Within a LA each cell has a unique cell identifier 16 bit. The same happens during and after handover. Sure the probability of having several channels available is much lower than having a single channel.. This second authentication is much stronger compared to the PIN.
Authentication with the system uses a challenge response scheme with a shared secret on the SIM and in the AuC. For GPRS data rates fluctuate anyway depending on the current load. CI uniquely identifies a cell worldwide global cell identity. This is because the operator is not really interested in who is using the system as long as it is a valid and paying customer.
For the typical steps and types of handover see figures 4. Otherwise the available bandwidth will decrease. This is done using a simple PIN. The best average delay is 0. UMTS introduces full authentication of all components.. HSCSD combines several time-slots but leaves coding untouched.
Assuming a data rate of TCP allows for fair sharing of bandwidth as soon as it is in stable state. GSM does not provide strong encryption end-to-end or MS to the gateway into the fixed network. Independent of the coding and modulation schemes the complexity of handover signalling. This requires the reception of acknowledgements. While the standards in principle specify devices that use all 8 time-slots in both directions. GPRS can dynamically use several time-slots per frame plus offers 4 different coding schemes that allow for higher data rates per slot.
These data rates are achievable using a single time-slot per frame in a certain channel. TCP was made for streaming larger amounts of data. This opened ways to fake base stations. Using less FEC System designers decided for over-the-air encryption only as they thought that the system itself is trustworthy. Trunked radio systems are attractive because of special features like very fast connection setup sub second.
Although data bases have been defined. TCP either never gets an acknowledgement back during transmission to adapt sender characteristics only if the initial sending window is large enough. Existing systems for these special purposes are.. Most systems furthermore do not need accounting and billing mechanisms as they are simply connected to the fixed phone network or a PBX.
Chapter 9 lists several proposed changes to TCP e. Most scenarios do not require complicated handover although possible in DECT.
Users can also apply SDM by placing access points further apart. Compared to GSM the system is simpler. All the multiplexing schemes together result in very high capacities of the system.
Under these conditions.. Real measurements with GPRS exhibit high latencies examples are round trip times for different packet sizes. TCP performs poorly. Higher cell capacities and higher data rates are mainly achieved by more powerful modulation schemes.
Trunked radio systems can be cheaper compared to GSM as they can have higher coverage with fewer base stations due to the lower expected load. Some operators already dropped out. After a much discussed licensing process beauty contests and auctions many operators are currently deploying 3G systems. UMTS implements asymmetrical data rates and different data rates in the same direction via different spreading factors.
Start of the system was As the chipping rate of UMTS is always constant. This makes it very difficult to cooperate for. CDMA as additional multiplexing scheme. Right now no one believes in a common worldwide system. Although licensing did not prescribe the usage of UMTS. The more the data is spread the lower the data rate is. The situation in the US and Canada is quite unclear. In the FDD mode adjusting the spreading factor is the only way for offering different data rates.
Release 4. There are also some cdma-operators in China which might opt for cdma KDDI deploys a cdma system.
Two different 3G systems are available in Japan. Already today many systems exist in parallel without a clear winner compared to GSM in Europe. If users want to send with a data rate in-between the system either drops data which can be recovered using FEC or inserts dummy data.
The cdma-operators will go for cdma TDD offers additionally the possibility of requesting more or less slots for up or downlink. While most 2G users today use GSM creating the biggest national market for this system. Geostationary satellites are only possible over the Equator. Depending on the location of the handover between two antennas at the same Node B.
In GSM this is no problem as it never happens that two stations send at the same time on the same frequency. Satellite systems 5. The rake receivers can thus handle both. Thousands of fibres through all oceans connect all continents offering more capacity than currently needed.
This is very high compared to delays in fibre optics.. Nothing can change this fact as currently the speed of light is the upper limit for the signal propagation speed and the distance of the GEOs is almost the circumference of the earth. For CDMA receiving signals from different base stations looks like multipath propagation. The handover is then as soft as a change in the strongest signals in a multipath scenario.
High elevations are also required in urban or mountainous areas where buildings or mountains block signals from satellites with low elevation. The lower the elevation the longer is the way for the signals through the atmosphere. Without beam forming high output power is needed. Satellites seem to be pinned to the sky. The elevation determines the signal quality.
The next step came with digital signals. Satellites can perform data forwarding functions depending on receiver addresses and can even route data through space from satellite to satellite.
This includes regeneration of the digital data and transmission of signals representation the received data without noise compared to analogue amplifiers that also amplify noise. Satellite could then work as repeater.
GEOs have to use the common orbit at km. They must not block their position. This is also the reason why all satellites must spare some propellant to catapult them out of the orbit after their lifetime. But also within individual web pages common parts commercials..
Asia etc. Broadcast systems 6. Satellite systems 5. Today, this traditional usage for satellites is not dominant anymore. Thousands of fibres through all oceans connect all continents offering more capacity than currently needed. This is very high compared to delays in fibre optics. Nothing can change this fact as currently the speed of light is the upper limit for the signal propagation speed and the distance of the GEOs is almost the circumference of the earth.
At an inclination of 0 the equator is covered. With a 90 inclination a satellite orbits over the poles. Geostationary satellites are only possible over the Equator, but then reception is poor at higher latitudes.
The elevation determines the signal quality. At an elevation of 0 reception is almost impossible. Typically, a signal has a usable quality starting from an elevation of Optimum signal quality can be achieved at High elevations are also required in urban or mountainous areas where buildings or mountains block signals from satellites with low elevation.
LEO: low orbiting satellites; pros: low delay, lower transmission power, intersatellite routing; cons: high complexity, high system cost MEO: somewhere in-between GEO and MEO HEO: non-circular orbits; pros: higher capacity over certain points; cons: complex systems 5.
The lower the elevation the longer is the way for the signals through the atmosphere. Without beam forming high output power is needed. The next step came with digital signals. Satellite could then work as repeater. This includes regeneration of the digital data and transmission of signals representation the received data without noise compared to analogue amplifiers that also amplify noise. Many of todays satellites are repeaters.
Satellites can perform data forwarding functions depending on receiver addresses and can even route data through space from satellite to satellite. Satellite signals are typically too weak to penetrate roofs. Furthermore, satellite phones often require a line-of-sight even outdoor. Thus, skyscrapers blocking the LOS may block communication, too.
Furthermore, the inclination must be 0. This leads to satellites stringed on this orbit like stones on a thread. Additionally, the satellites should orbit above populated regions.
Thus, areas above the equator looking towards Europe, America, Asia etc. This is also the reason why all satellites must spare some propellant to catapult them out of the orbit after their lifetime. They must not block their position. Broadcast systems 6. Thus, broadcast systems are good for distributing mass data relevant to many in the best case all users. Good examples are radio and TV, but also system updates, popular web content, news etc.
Typically, it is to expensive to broadcast individual data. However, if broadcast bandwidth is available this is feasible, too. In particular if downloads are needed at higher relative speeds. Mobile phone systems have to lower their bandwidth dramatically at high speeds, while broadcast systems may still work at full bandwidth.
But also within individual web pages common parts commercials, video streams could use broadcast systems, while the individual parts use mobile telecommunication systems. Depending on the current location, the LBS may program broadcast disks of broadcast providers for individual users or groups of users.
If an LBS discovers a group of people standing in front of a museum, it could trigger a video stream on a DVB device showing pictures from the current exhibition. Wireless LAN 7.
In order to support roaming additional inter access point protocols are needed. The access points have to inform each other about the current active stations within their coverage. This approach is only feasible for local areas, otherwise location registers etc. The access points simply operate as transparent, self-learning bridges that need additional information to forget stations faster compared to the aging mechanisms in fixed network bridges.
Station identification is based on MAC addresses. Roaming typically requires a switched layernetwork. Common characteristics: similar propagation characteristics, similar problems. Thus, many WLAN standards introduce more or less strong encryption mechanisms. The most famous one, WEP, has been cracked soon after introduction.
Furthermore, the most prominent WLAN family, New standards introduce more security Bluetooth on the other hand implements all functions in all nodes enabling all devices to set up a network.
Main focus of HiperLAN2 is the infrastructure mode, too. Roughly, it can be said that Another advantage is the simple protection from eavesdropping. Attackers can much more easily tap Bluetooth communication, incautious users even let their Bluetooth devices open for public access simply scan for Bluetooth devices at public devices - many are detectable. IR communication is much more secure as the devices have to face each other directed IR.
Depending on transmission technology, bandwidth etc. They all share a common MAC. All Bluetooth systems use the same layers. In particular Bluetooth systems offer several low power modes as they are typically battery operated. Negative effects of power saving are the increased latency for spontaneous transmissions the devices have to wake-up first. Thus, the shorter access delay should be the less power a device can save.
Furthermore, high data rates require high power. If the periodic sleep function is not synchronised with, e. HiperLAN2, on the contrary, establishes a central controller for the ad-hoc mode called direct mode , which controls QoS.
Bluetooth always works ad-hoc, well, a master controls up to seven slaves and, thus, forms an ad-hoc access point. Bluetooth therefore can offer QoS in its ad-hoc mode. QoS in Bluetooth is provided by periodic polling through the master. This guarantees certain data rates and access latencies. After a master has been found, Bluetooth can give hard guarantees for SCO connections. As soon as there is a contention phase, the system cannot guarantee access latencies.
For HiperLAN2 this problem does not exist as the access point controls all medium access. If a terminal is hidden it cannot communicate at all and, thus, does not interfere. In Bluetooth, too, are no hidden terminals as the master controls all visible slaves. If a terminal does not see the master it cannot participate in communication. If this terminal sends anyway it will not interfere as this terminal then acts as master with a different hopping sequence.
If all systems behave well this mechanism gives a fair share of the overall bandwidth to all stations. Fairness then depends on these special nodes, which also decide upon the waiting time of a packet when it will be transmitted.
In However, in order to access the access point, nodes may transmit during a random access phase in HiperLAN2 random channel with feedback from the access point. At this point collisions may occur on the MAC layer. For The MAC algorithm with back-off solves this problem. Collisions on the PHY layer may occur in Bluetooth only if another piconet randomly jumps to the same frequency at the same time.
This will destroy data for this time-slot. In HiperLAN2 different networks are separated in frequency, thus there should be not collisions besides the above mentioned during the random access phase. Important packets in Thus, The system breaks down at high load as then only collisions will occur and no station is able to send anything.
Therefore, HiperLAN2 and Bluetooth require some kind of connection setup. This increases access latency even if the load is light or zero.
As soon as a connection exists, the quality and access latency is almost independent of the load. Both systems can be loaded to the maximum without a system breakdown. For Bluetooth this is true in a piconet, not within scatternets. Scalability is low in general 8 nodes within a piconet. Nodes changing piconets have to resynchronise to the new piconet, there is no signalling between masters for roaming nodes.
Typically, inter access point protocols are available in infrastructure networks only there could be something like a masterto-master protocol in Bluetooth. For adhoc networks the overhead would be too much. Roaming support is typically via self-learning bridges exchanging their filtering databases which MAC address is visible at which bridge.
This also requires authentication in both networks, nodes that are almost always active and synchronous clocks if the master jumps into another piconet. If the master jumps away all network traffic in the piconet stops, all slaves have to wait until the master returns. All hopping sequences must stay synchronous during that time.
Up to now not many devices are capable of forming scatternets with nodes jumping back and forth. ATM was seen as the big unifying technology handling all different types of traffic with QoS. Well, in principle this is still true, however, it turned out that this technology is much too complicated for many applications but it is still dominant in WANs. ATM offers hard QoS, end-to-end. Most applications of today can adapt to the varying quality of the Internet.
Mobile network layer 8. Main problems are the high dynamicity Internet routing protocols like the standard fixed network routing protocols in classical phone networks have never been designed for roaming nodes, not to mention mobile routers.
Without additional functions addressing fails, nodes would use topological incorrect addresses etc. Standard routing protocols from the Internet e. But then no correspondent node can find the mobile node or a lot of signalling this current IP address would be necessary. Alternatively, all routers could change routing table to reflect the current location of the mobile node. This obviously does neither scale nor is it secure changing routing entries destabilises the whole network.
Although mobile IP tries to provide transparency of mobility it cannot hide, e. However, mobility is transparent if only best-effort transmission is considered. Scalability, too, is a problem as soon as many nodes move between subnets.
Mobile IP causes a big overhead due to registration messages. This is one of the reasons for micro mobility supporting approaches. Security is also problematic, as topological incorrect addresses do not work together with firewalls and route optimisation reveals location.
This is needed to make mobility transparent the inner data packet should not notice data transfer through the tunnel, thus TTL remains untouched. Layer 2 registration is handled by, e. If available on layer 2 the MN could detach from the old access point after attaching to the new one. It would first set-up a layer two association and listen for agent advertisements. Alternatively, it could send agent solicitations. After receiving the advertisement and attaching to a new FA authentication could start.
Concurrently, the FA could inform the old FA about the node. See figure 8. The packet is thus payload of the outer packet inside the tunnel. This is simple because all devices already know how to insert payload into an IP packet. Bandwidth is wasted by transferring the same field several times. Minimal encapsulation tries to avoid this waste of bandwidth, however, it cannot be used in case of fragmentation.
GRE is a more general scheme, not only for IP traffic but also, e. Additionally, it may control the level of encapsulation. Several versions exist. One optimisation is the binding update at the CN. This lets the CN directly send its data to the MN. This solution reveals the current location of the MN and is not transparent anymore the CN now knows that the MN is mobile, furthermore, it knows the location via the COA. An explicit FA is not needed any more, all routers are capable of agent advertisements, tunnelling, forwarding of data, setting up security associations.
Authentication is built-in as well as optimisation functions.
The only additional security related function is the authentication of MN and HA. Firewalls and mobile IP do not really go together. Either reverse tunnelling or tunnelling in general drills a hole in the firewall or MNs can not operate in foreign networks.
The firewall has to be integrated into the security solution. IP does not support QoS. Furthermore, packets requiring certain QoS must be treated according to these requirements also inside the tunnel. Parameters acquired via DHCP are, e. Without DHCP all parameters must be configured manually. Popular Files. January June Trending on EasyEngineering. Vijayaraghavan, L. Gopinath, Lakshmi Publications Book Free November December October 2.
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