[Κινητές και Δορυφορικές] Γενικές απορίες κι ανακοινώσεις/επικαιρότητα 2013/2014

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Είσαι πρωτοετής;... Καλώς ήρθες! Μπορείς να βρεις πληροφορίες εδώ. Βοήθεια για τους καινούργιους μέσω χάρτη.

Κατεβάστε εδώ το Android Application για εύκολη πρόσβαση στο forum.

Ανεβάζετε τα θέματα των εξετάσεων στον τομέα Downloads με προσοχή στα ονόματα των αρχείων!

[12:00-13:30]

Η γραμματεία είναι ανοιχτή καθημερινά 12:00-13:30

[ampoulog]

4G LTE-Advanced Technology Overview

4G LTE refers to the evolved version of LTE that is being developed by 3GPP to meet or exceed the requirements of the International Telecommunication Union (ITU) for a true fourth generation radio-communication standard known as IMT-Advanced. 4G LTE, whose project name is LTE-Advanced, is being specified initially in Release 10 of the 3GPP standard, with a functional freeze targeted for March 2011. The 4G LTE standard will continue to be developed in subsequent releases. In October 2009, the 3GPP Partners formally submitted LTE-Advanced to the ITU as a candidate for 4G IMT-Advanced1. The certified technology specifications for IMT-Advanced are expected to be published in early 20112.

Key ITU requirements for IMT-Advanced that 4G LTE will support include the following3:

A high degree of common functionality worldwide while retaining the flexibility to support a wide range of local services and applications in a cost-efficient manner
Compatibility of services within IMT and with fixed networks
Capability for interworking with other radio systems
High quality mobile services
User equipment suitable for worldwide use
User-friendly applications, services, and equipment
Worldwide roaming capability
Enhanced peak data rates to support advanced mobile services and applications (100 Mbps for high mobility and 1 Gbps for low mobility)
3GPP cites an additional reason to align 4G LTE with IMT-Advanced: IMT-conformant systems will be candidates for any new spectrum bands identified by the WRC-07 (World Radiocommunication Conference). 4

3GPP Considerations

3GPP Technical Report (TR) 36.913, "Requirements for Further Advancements for E-UTRA (LTE-Advanced)," describes the requirements for further advancement of the LTE E-UTRA (air interface) and E-UTRAN (air interface network).5 These requirements are based on those of the ITU for IMT-Advanced as well as on 3GPP operators' own requirements for advancing LTE. Major technical considerations for 4G LTE development include:

Continual improvement to the LTE radio technology and architecture
Scenarios and performance requirements for interworking with legacy radio access technologies
Backward compatibility of LTE-Advanced with LTE. An LTE terminal should be able to work in an LTE-Advanced network and vice versa. Any exceptions will be considered by 3GPP.
Account taken of recent WRC-07 decisions for new IMT spectrum as well as existing frequency bands to ensure that LTE-Advanced geographically accommodates available spectrum for channel allocations above 20 MHz. Also, requirements must recognize those parts of the world in which wideband channels are not available.
System performance requirements

The system performance requirements for 4G-LTE will in most cases exceed those of IMT-Advanced. The 1 Gbps peak data rate required by the ITU will be achieved in 4G LTE using 4x4 MIMO and transmission bandwidth wider than approximately 70 MHz. In terms of spectral efficiency, today's LTE (Release 8) satisfies the IMT-Advanced requirement for the downlink, but the bps/Hz must be doubled in LTE-Advanced to meet the 4G requirement.


Table 1 compares the spectral efficiency targets for LTE, LTE-Advanced, and IMT-Advanced. Note that the peak rates for LTE-Advanced are substantially higher than the IMT-Advanced requirements, which highlights a desire to drive up peak performance in 4G LTE, although targets for average performance are closer to ITU requirements. However, TR 36.913 states that targets for average spectral efficiency and for cell-edge user throughput efficiency should be given higher priority than targets for peak spectral efficiency and other features such as VoIP capacity.5 Thus 4G LTE work will be focused on the challenges of raising average and cell-edge performance.

Table 1. Performance targets for LTE, Advanced-LTE, and IMT-Advanced6



Performance targets for LTE Advanced-LTE IMT Advanced

White Space

The flexibility of spectrum is another important consideration. Actual available spectra differ by region and country. 3GPP is studying the feasibility of various deployment scenarios for spectrum allocation.

3GPP solution proposals

Proposed solutions for achieving LTE-Advanced performance targets are defined in 3GPP TR 36.814, "Further Advancements for E-UTRA Physical Layer Aspects."7 The following features are supported in LTE-Advanced proposals:

Carrier and spectrum aggregation--The lack of contiguous spectrum for wider transmission bandwidths (to 100 MHz) forces the use of carrier aggregation to meet peak data rate and spectrum flexibility requirements. Aggregation of contiguous and non-contiguous component carriers is allowed.
Enhanced uplink multiple access--The addition of N-times DFT-spread OFDM (also known as "clustered SC-FDMA") will satisfy increased data rate requirements while maintaining backward-compatibility with LTE.
Higher order MIMO transmission--Up to 8x8 MIMO in the downlink and 4x4 MIMO in the uplink is used to reach peak data rates. Beamforming with spatial multiplexing is being considered to increase data rates, coverage, and capacity.
Coordinated multipoint (CoMP) transmission and reception--This MIMO variant is intended to improve performance for high data rates, cell‐edge throughput, and system throughput. Is being studied for Release 11.
Relaying--In-channel relays receive, amplify, and retransmit downlink and uplink signals to improve coverage. More advanced relaying enables the use of some subframes in a channel to carry backhaul traffic. The main use cases for relays are to improve urban or indoor throughput, to add dead zone coverage, or to extend coverage in rural areas.
Other proposals related to 4G LTE address the support needs of an increasingly heterogeneous network that combines macro-, micro-, pico-, and femtocells, along with repeaters and relay nodes. Work is ongoing to develop advanced methods of radio resource management including new self-optimizing network (SON) features. The 4G LTE specifications also continue to focus on the use of femtocells and home base stations (eNBs) as a means of improving network efficiencies and reducing infrastructure costs.

Industry-supported field trials are already demonstrating the viability of many of the technical concepts in LTE-Advanced, and 3GPP's submission to the ITU included a self-evaluation of its proposals concluding that LTE-Advanced meets all IMT-Advanced requirements for being officially certified as 4G. Nevertheless, the timing of 4G LTE deployment is difficult to predict and will likely be dependent on industry demand and the success of today's Release 8 and 9 LTE rollouts.

Design and test challenges

As an evolution of LTE, LTE-Advanced will pose similar challenges to design and test engineers. The LTE standard is new and quite complex, with multiple channel bandwidths, different transmission schemes for the downlink and uplink, both frequency and time domain duplexing (FDD and TDD) transmission modes, and use of MIMO antenna techniques. LTE and LTE-Advanced will likely have to co-exist with 2G and 3G cellular systems for some time, so interworking necessities and potential interference remain important issues. In a difficult radio environment, LTE sets the bar for performance targets very high, and LTE-Advanced raises it even higher.

Some new challenges are anticipated with the solutions proposals for LTE-Advanced. For example, carrier aggregation will undoubtedly pose major difficulties for the UE, which must handle multiple simultaneous transmit and receive chains. The addition of simultaneous non-contiguous transmitters create a highly challenging radio environment in terms of spur management and self-blocking. Simultaneous transmit or receive with mandatory MIMO support will add significantly to the challenge of antenna design.

The introduction of clustered SC-FDMA in the uplink allows frequency selective scheduling within a component carrier for better link performance, and the PUCCH and PUSCH can be scheduled together to reduce latency. However, clustered SC-FDMA increases peak to average power ratio (PAR) by several dB, adding to transmitter linearity issues. Simultaneous PUCCH and PUSCH also increase PAR. Both features create multi-carrier signals within the channel bandwidth and increase the opportunity for in-channel and adjacent channel spur generation. Test tools will need to be enhanced with capability for signal generation and analysis of multicarrier signals in 4G power amplifiers.

Higher order MIMO will increase the need for simultaneous transceivers in a manner similar to carrier aggregation. However, MIMO has an additional challenge in that the number of antennas will multiply, and the MIMO antennas will have to be de-correlated. It will be especially difficult to design multiband, MIMO antennas with good de-correlation to operate in the small space of a 4G UE. Conducted testing of higher order MIMO terminals will no longer be usable for predicting actual radiated performance in an operational network. A study item in Release 9 of the 3GPP standard is looking at MIMO over the air testing as an alternative.

From the UE perspective, relaying is completely transparent. In this case the challenge is all on the network side. For the system to work, the link budget from the relay node to the macro eNB must be good, which implies line of site positioning. The main operational challenge in getting relaying to work will be in the management of the UE. The UE must be instructed to hand over to a relay node that is within range and release the relay node when the UE goes out of range. If this process is not well managed, the performance of the cell could actually go down, not up as intended.

These are just a few of the challenges that 4G LTE will present wireless design and test engineers. As the 4G specifications are published and the certification process moves ahead, so too will test vendors have to increase the capability of their products and invent ingenious new ways to verify the performance of the evolving 4G systems.

1 Press release, "3GPP Partners propose IMT-Advanced radio," Geneva, October 8, 2009.

2 3GPP Americas, "Mobile Broadband Innovation Path to 4G: Release 9, Release 10 and Beyond," www.3Gamericas.org

3 ITU-R M [IMT-TECH], "Requirements related to technical performance for IMT-Advanced radio interface(s)," August 2008.

4 3GPP web site, 3GPP - LTE-Advanced. 3GPP - LTE-Advanced

5 3GPP TR 36.913 V9.0.0 (2009-12), www.3gpp.org/ftp/Specs/archive/36_series/36.913

6 Rumney, Moray. LTE and the Evolution to 4G Wireless: Design and Measurement Challenges, p.416. 2009, Agilent Technologies Publication.

7 3GPP TR 36.814, www.3gpp.org/ftp/Specs/archive/36_series/36.814/


Source: http://www.home.agilent.com/agilent/editorial.jspx?ckey=1905163&id=1905163%22&lc=eng&cc=IN

[ampoulog]

Σχετικά με την Εργασία και την Παρουσίαση

Η παρουσίαση την Τρίτη 13.00 - 15.00 είναι υποχρεωτική και δεν μπορεί να υπάρξει αναβολή. Οι ομάδες θα πρέπει να έχουν ετοιμάσει μία παρουσίαση διάρκειας 10-15' το πολύ (~10-15 διαφάνειες) στις οποίες αν δεν έχουν ολοκληρώσει την εργασία θα συμπεριλάβουν τα:
- πρόβλημα που εξετάζουν και ανάγκη επίλυσης (π.χ. Ποια η ανάγκη για Channel Estimation ή Sychronization)
- μοντέλο του συστήματος που εξετάζουν (SISO OFDM με block που θα δείχνουν που θα εφαρμόσουν (-ζουν) τις διάφορες τεχνικές)
- σύντομη παρουσίαση των καναλιών που έχουν και πως τα υλοποίησαν
- τεχνικές που θα χρησιμοποιήσουν και τι έχουν υλοποιήσει από αυτές
- ότι αποτελέσματα έχουν πάρει
Καλό είναι να αναφερθούν σε "κολλήματα" και προβλήματα που έχουν τόσο στις τεχνικές όσο και στην υλοποίηση, ώστε να γίνει συζήτηση και να βρεθούν λύσεις που θα σας βοηθήσουν να ολοκληρώσετε την εργασία.

Το παραπάνω αποτελεί μία γενική πρόταση στο πως μπορείτε να δομήσετε την παρουσίαση σας. Μπορείτε να ξεφύγετε όσο θέλετε. 

Συμπληρωματικά:

Οι  ομάδες  που  ασχολούνται  με  την  εργασία  καλούνται  να  στείλουν  mail  στο  ampoulog@auth.gr  για  την  επιβεβαίωση  της  παρουσίασης  ή  να  το  δηλώσουν  στο  μάθημα  της  Δευτέρας  13/01/2014. 

Επίσης,  έως  και  μία  ώρα  πριν  την  παρουσίαση  οι  ομάδες  θα  πρέπει  να  στείλουν  τις  διαφάνειες  στο  παραπάνω  e-mail  σε  μορφή  .ppt,  .pptx,  .odp  ή  ο,τι  άλλο  θέλουν,  αλλά  και  .pdf,  διαφορετικά  θα  πρέπει  να  φροντίσουν  να  έχουν  την  παρουσίαση  μαζί  τους  σε  flash  drive.     

[ampoulog]

Για εφαρμογές (και όχι μόνο) του OFDM:
http://web.ee.ccu.edu.tw/~wl/ofdm/pdfnew/Chapter%208%20OFDM%20Applications.pdf
http://iosrjournals.org/iosr-jmce/papers/vol1-issue1/B0110711.pdf
http://engold.ui.ac.ir/~sabahi/Advanced%20digital%20communication/OFDM%20and%20Its%20Wireless%20Applications-%20A%20Survey.pdf
http://www.altera.com/literature/an/an503.pdf


Για όποιον ενδιαφέρεται να δει και κάποιες πιο ενεργειακές εφαρμογές του OFDM.


OFDM-Based High Speed Narrowband PLC Approved for Smart Metering and Smart Grids

Παρουσίαση στο: http://cms.comsoc.org/SiteGen/Uploads/Public/Docs_ISPLC_2009_/keynotes/2009-03-30_ISPLC-Keynote_V1d.pdf

και:
http://www.maximintegrated.com/products/powerline/pdfs/G3-PLC-Physical-Layer-Specification.pdf
http://www.idosi.org/wasj/wasj20(9)12/6.pdf

[ampoulog]

Στο υλικό μαθήματος -> Πρόσθετες σημειώσεις θεωρίας μπορείτε να βρείτε κάποια επιπλέον πράγματα για OFDM.

[ampoulog]

Cooperative Communication in Wireless Networks

Για όσους ενδιαφέρονται για Cooperative Communications!

link: http://xanthippi.ceid.upatras.gr/courses/mobile/2006_07/Cooperative.pdf

[ampoulog]

Cooperative Communications in Resource-Constrained Wireless Networks

link: http://xanthippi.ceid.upatras.gr/courses/mobile/2009_10/cooperative_resource.pdf

[ampoulog]

Cooperative Communications in Mobile Ad-Hoc Networks: Rethinking the Link Abstraction

link: http://www3.nd.edu/~jnl/pubs/crc-coop-chapter.pdf

[ampoulog]

Υπενθύμιση!

Σχετικά με την Εργασία και την Παρουσίαση

Η παρουσίαση την Τρίτη 13.00 - 15.00 είναι υποχρεωτική και δεν μπορεί να υπάρξει αναβολή. Οι ομάδες θα πρέπει να έχουν ετοιμάσει μία παρουσίαση διάρκειας 10-15' το πολύ (~10-15 διαφάνειες) στις οποίες αν δεν έχουν ολοκληρώσει την εργασία θα συμπεριλάβουν τα:
- πρόβλημα που εξετάζουν και ανάγκη επίλυσης (π.χ. Ποια η ανάγκη για Channel Estimation ή Sychronization)
- μοντέλο του συστήματος που εξετάζουν (SISO OFDM με block που θα δείχνουν που θα εφαρμόσουν (-ζουν) τις διάφορες τεχνικές)
- σύντομη παρουσίαση των καναλιών που έχουν και πως τα υλοποίησαν
- τεχνικές που θα χρησιμοποιήσουν και τι έχουν υλοποιήσει από αυτές
- ότι αποτελέσματα έχουν πάρει
Καλό είναι να αναφερθούν σε "κολλήματα" και προβλήματα που έχουν τόσο στις τεχνικές όσο και στην υλοποίηση, ώστε να γίνει συζήτηση και να βρεθούν λύσεις που θα σας βοηθήσουν να ολοκληρώσετε την εργασία.

Το παραπάνω αποτελεί μία γενική πρόταση στο πως μπορείτε να δομήσετε την παρουσίαση σας. Μπορείτε να ξεφύγετε όσο θέλετε. 

Συμπληρωματικά:

Οι  ομάδες  που  ασχολούνται  με  την  εργασία  καλούνται  να  στείλουν  mail  στο  ampoulog@auth.gr  για  την  επιβεβαίωση  της  παρουσίασης  ή  να  το  δηλώσουν  στο  μάθημα  της  Δευτέρας  13/01/2014. 

Επίσης,  έως  και  μία  ώρα  πριν  την  παρουσίαση  οι  ομάδες  θα  πρέπει  να  στείλουν  τις  διαφάνειες  στο  παραπάνω  e-mail  σε  μορφή  .ppt,  .pptx,  .odp  ή  ο,τι  άλλο  θέλουν,  αλλά  και  .pdf,  διαφορετικά  θα  πρέπει  να  φροντίσουν  να  έχουν  την  παρουσίαση  μαζί  τους  σε  flash  drive.     

[odynik]

Καλησπέρα.

Το βιβλίο που παραθέτω μου φάνηκε ιδιαίτερα επικοδομητικό και πιστεύω ότι μπορεί να βοηθήσει και εσάς όχι μόνο στην μελέτη αλλά και στην εργασία.

Μπορείτε να δείτε ένα preview πριν το κατεβάσετε: http://books.google.gr/books/about/MIMO_OFDM_Wireless_Communications_with_M.html?id=6HwAoeuMr3kC&redir_esc=y

[Lampros]

τι έγινε?
δεν πρόλαβα να το κατεβάσω και διαγράφηκε

[odynik]

Έκανα βλακεία με τα πνευματικά δικαιώματα και τα σχετικά...

Αλλά για ρίξτε μια ματιά εδώ, http://www.freebookspot.es/

Ο δικός μου τρόπος,

(Είναι πιο εύκολος από ότι φαίνεται)

Έχετε τα στοιχεία του βιβλίου (http://books.google.gr/books/about/MIMO_OFDM_Wireless_Communications_with_M.html?id=6HwAoeuMr3kC&redir_esc=y)
Έχετε την πηγή(http://www.freebookspot.es/).
Μόλις το βρείτε θα σας βγάλει μια λίστα με links(i.e. http://ryushare.com/ea492c9a57d/04708256...)
Αυτό το link σας κάνει redirect σε μια σελίδα όπου μπορείτε να το κατεβάσετε.
Σε αυτή την σελίδα κάν'τε scroll down και βρείτε ένα κουμπί που λέει "Low Speed Download"
Περιμένετε ένα λεπτό.
Μετά βάλτε την λέξη που σας ζητάει για να τσεκάρει εάν είστε botακι.
Μετά θα δημιουργήσει ένα link για να κάνετε Download.

Φυσικά μπορείτε να κάνετε τα δικά σας και να το βρείτε μέσα από τις δικές σας πηγές.(ΗΜΜΥ είστε)

Σε περίπτωση που δεν τα καταφέρετε πάλι υπάρχει τρόπος...Στο μάθημα!

[ampoulog]

Heterogeneous Networks in LTE

by Jeanette Wannstrom, masterltefaster.com and Keith Mallinson, WiseHarbor

Effective network planning is essential to cope with the increasing number of mobile broadband data subscribers and bandwidth-intensive services competing for limited radio resources. Operators have met this challenge by increasing capacity with new radio spectrum, adding multi-antenna techniques and implementing more efficient modulation and coding schemes. However, these measures alone are insufficient in the most crowded environments and at cell edges where performance can significantly degrade. Operators are also adding small cells and tightly-integrating these with their macro networks to spread traffic loads, widely maintain performance and service quality while reusing spectrum most efficiently.

One way to expand an existing macro-network, while maintaining it as a homogeneous network, is to “densify” it by adding more sectors per eNB or deploying more macro-eNBs. However, reducing the site-to-site distance in the macro-network can only be pursued to a certain extent because finding new macro-sites becomes increasingly difficult and can be expensive, especially in city centres. An alternative is to introduce small cells through the addition of low-power base stations (eNBs, HeNBs or Relay Nodes (RNs)) or Remote Radio Heads (RRH) to existing macro-eNBs. Site acquisition is easier and cheaper with this equipment which is also correspondingly smaller.

Small cells are primarily added to increase capacity in hot spots with high user demand and to fill in areas not covered by the macro network – both outdoors and indoors. They also improve network performance and service quality by offloading from the large macro-cells. The result is a heterogeneous network with large macro-cells in combination with small cells providing increased bitrates per unit area. See Figure 1.



Heterogeneous network planning was already used in GSM. The large and small cells in GSM are separated through the use of different frequencies. This solution is still possible in LTE. However, LTE networks mainly use a frequency reuse of one to maximize utilization of the licensed bandwidth.

In heterogeneous networks the cells of different sizes are referred to as macro-, micro-, pico- and femto-cells; listed in order of decreasing base station power. The actual cell size depends not only on the eNB power but also on antenna position, as well as the location environment; e.g. rural or city, indoor or outdoor . The HeNB (Home eNB) was introduced in LTE Release 9 (R9). It is a low power eNB which is mainly used to provide indoor coverage, femto-cells, for Closed Subscriber Groups (CSG), for example, in office premises. See Figure 2.

Specific to HeNBs, is that they are privately owned and deployed without coordination with the macro-network. If the frequency used in the femto-cell is the same as the frequency used in the macro-cells, and the femto-cell is only used for CSG, then there is a risk of interference between the femto-cell and the surrounding network.

The Relay Node (RN) is another type of low-power base station added to the LTE R10 specifications. The RN is connected to a Donor eNB (DeNB) via the Un radio interface, which is based on the LTE Uu interface. See Figure 2. When the frequencies used on Uu and Un for the RN are the same, there is a risk of self interference in the RN. From the UE perspective the RN will act as an eNB, and from the DeNB’s view the RN will be seen as a UE. As also mentioned, RRHs connected to an eNB via fibre can be used to provide small cell coverage.



Introducing a mix of cell sizes and generating a heterogeneous network adds to the complexity of network planning. In a network with a frequency reuse of one, the UE normally camps on the cell with the strongest received DL signal (SSDL), hence the border between two cells is located at the point where SSDL is the same in both cells. In homogeneous networks, this also typically coincides with the point of equal path loss for the UL (PLUL) in both cells. In a heterogeneous network, with high-power nodes in the large cells and low-power nodes in the small cells, the point of equal SSDL will not necessarily be the same as that of equal PLUL. See Figure 3.



A major issue in heterogeneous network planning is to ensure that the small cells actually serve enough users. One way to do that is to increase the area served by the small cell, which can be done through the use of a positive cell selection offset to the SSDL of the small cell. This is called Cell Range Extension (CRE). See Figure 4.

http://www.3gpp.org/images/articleimages/Hetnet/fig004.jpg

A negative effect of this is the increased interference on the DL experienced by the UE located in the CRE region and served by the base station in the small cell. This may impact the reception of the DL control channels in particular.



Περισσότερα στο: http://www.3gpp.org/technologies/keywords-acronyms/1576-hetnet

[ampoulog]

Παρακαλούνται  οι  φοιτητές  που  παρακολούθησαν  το  μάθημα  να  συμπληρώσουν    ηλεκτρονικά  το  δελτίο  αξιολόγησης  του  μαθήματος  μέχρι  τις  19/2/2014.   

Η  συμπλήρωση  του  δελτίου  μπορεί  να  γίνει  από  την  ιστοσελίδα  της  ΜΟΔΙΠ    (http://qa.auth.gr)  κάνοντας  "ΕΙΣΟΔΟ"    στο  σύστημα  με  τον  πανεπιστημιακό  σας  λογαριασμό  και  επιλέγοντας  Ηλεκτρονική  αξιολόγηση  ή  απευθείας  μέσω  του  συνδέσμου  (https://login-idp.auth.gr/idp/Authn/UserPassword).

[ampoulog]

http://www.youtube.com/watch?v=ATswqszCuMI

[ampoulog]

http://www.youtube.com/watch?v=P7nhgX0ppek

http://www.youtube.com/watch?v=Wn-BV9Zp8Pk

http://www.youtube.com/watch?v=JpzAFb30lKk

http://www.youtube.com/watch?v=yxYzjHBKNcA

http://www.youtube.com/watch?v=_vfzAL5L29Y

http://www.youtube.com/watch?v=QPydHE3a8Kw