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Reducing Physical Layer Control Signaling Using Mobile-Assisted Scheduling
Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.ORCID iD: 0000-0002-7599-4367
2013 (English)In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 12, no 1, 368-379 p.Article in journal (Refereed) Published
Abstract [en]

We present a scheme for reducing the part of the downlink signaling  traffic in wireless multiple access systems that contains scheduling  information.  The theoretical basis of the scheme is that the  scheduling decisions made by the base station are correlated with  the CSI reports from the mobiles.  This correlation can be exploited  by the source coding scheme that is used to compress the scheduling  maps before they are sent to the mobiles. In the proposed scheme,  this idea is implemented by letting the mobiles make tentative  scheduling decisions themselves, and then letting the base station  transmit "agreement maps" instead of raw scheduling maps to the  mobiles.  The agreement maps have lower entropy and they require  less resources to be transmitted than the original scheduling maps  do. The improvement can be substantial.  We also model the task of  finding the optimal scheduling assignments according to the proposed  scheme as a combinatorial optimization problem and present an  efficient algorithm to find the optimal solution.

Place, publisher, year, edition, pages
IEEE , 2013. Vol. 12, no 1, 368-379 p.
Keyword [en]
Mobile-assisted scheduling; Control signaling; Resource allocation; Signaling overhead
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-68071DOI: 10.1109/TWC.2012.120312.120680ISI: 000314178100035OAI: oai:DiVA.org:liu-68071DiVA: diva2:416023
Available from: 2011-05-10 Created: 2011-05-10 Last updated: 2016-08-31
In thesis
1. Aspects of Control Signaling in Wireless Multiple Access Systems
Open this publication in new window or tab >>Aspects of Control Signaling in Wireless Multiple Access Systems
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

From its first appearance, wireless communications has changed thelife for many people worldwide. Currently, more than half of the world's population are using wireless devices for various purposes on a daily basis. While the early wireless systems could provide simple and specific low-rate services, today's systems can support a variety of more advanced services some of which require high data rate communications. This includes for example web-browsing and streaming multimedia applications. To meet the high demands on the current systems, many technical solutions have been proposed. Many of these solutions are powerful in the sense of boosting the system performance, but on the other hand, they impose a substantial control signaling overhead on the system. The control signaling refers to sending the control information that is necessary to establish and/or maintain the connection as opposed to the payload data that is transmitted during the connection.

In this thesis, we are interested in evaluating the relations between the gain of deploying new techniques and the amount of control signaling overhead they incur. Moreover we are interested in finding efficient algorithms that can potentially reduce the control signaling overhead. More specifically, we first focus on the part of the control signaling overhead that concerns sending the scheduling assignments that describe how the channel resources are allocated among the users. We compare two ways for the signaling of scheduling assignments and we will study how different parameters such as scheduling granularity impact the control signaling overhead. We also provide two schemes that reduce the control signaling overhead substantially. We then provide an algorithm for fast blind identification of channel codes. This algorithm is very useful in improving the so-called blind decoding performance. This is essential since blind decoding is used to achieve adaptive modulation and coding in the control channel of some of the wireless communication systems such as 3GPP Long Term Evolution.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2011. 22 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1493
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-68069 (URN)LIU-TEK-LIC-2011:32 (Local ID)978-91-7393-145-8 (ISBN)LIU-TEK-LIC-2011:32 (Archive number)LIU-TEK-LIC-2011:32 (OAI)
Presentation
2011-06-10, Planck, Fysik Huset, Campus Valla, Linköpings universitet, Linköping, 13:15 (English)
Opponent
Supervisors
Available from: 2011-05-12 Created: 2011-05-10 Last updated: 2016-08-31Bibliographically approved
2. Improving the Efficiency of Control Signaling in Wireless Multiple Access Systems
Open this publication in new window or tab >>Improving the Efficiency of Control Signaling in Wireless Multiple Access Systems
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Prior to the transmission of payload data in any multiple access system, there is generally a need to send control information such as scheduling assignments, transmission parameters and HARQ acknowledgments. This process is called control signaling and has a significant impact on the overall system performance. This dissertation considers different aspects of control signaling and proposes some novel schemes for improving it. The dissertation is split into two parts where in the first part the focus is on the transmission of scheduling assignments, and in the second part the focus is on improving the “blind decoding” process that is used to achieve adaptive coding and modulation in transmission of control information.

More specifically, in the first part of the dissertation we first compare the two conventional schemes for control signaling using extensive system simulations. In doing so, we use practical assumptions on the scheduling algorithm as well as on the compression and transmission of the scheduling information. We then provide two schemes for reducing the amount of control signaling that concerns the transmission of scheduling assignments. The first scheme, which is reminiscent of source coding with side information, uses the knowledge that each user has about its own channel condition to compress the scheduling information more effectively. The second scheme uses the fact that in wireless multiple access systems, a user with a given channel condition can in principle decode the data intended to the users that have weaker channels. Therefore, the idea is to send the scheduling information of different terminals in a differential manner starting from the user with the weakest channel and letting all the terminals overhear the transmission of one another. Finally, in the last section of this part we use some of the recent results in information theory to form a general framework for the comparison of different control signaling schemes. We formulate an optimization problem that for a given desired error probability finds the minimum required number of channel uses for a given signaling scheme.

In the second part of the thesis, we propose three schemes for reducing the complexity of the blind decoding process. The first one is a novel scheme for fast blind identification of channel codes. More precisely, we propose an efficient algorithm that for a given sequence of received symbols and a given linear channel code, finds the posterior probability that all the parity check relations of the code aresatisfied. We then use this quantity to perform a sequential statistical hypotheses test that reduces the computational complexity of blind decoding. The idea in the second scheme is to broadcast a control message prior to the transmission of control information to instruct only a subset of the terminals (ideally only those terminals that have been scheduled for reception of payload data and hence benefit from performing a blind search attempt) to perform blind search decoding, which can be used for instance in LTE to reduce the complexity of the blind decoding process. Finally, in the third scheme we propose to split the CRC, used by the terminals to find their control information, into two parts and inject one part early in the control data stream so that the terminals can detect early if the current decoding attempt will be successful, which ultimately reduces the blind decoding complexity.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2014. 36 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1556
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-102537 (URN)10.3384/diss.diva-102537 (DOI)978-91-7519-477-6 (print) (ISBN)
Public defence
2014-01-17, Visionen, B-huset, Campus Valla, Linköpings universitet, Linköping, 13:15 (English)
Opponent
Supervisors
Available from: 2013-12-13 Created: 2013-12-13 Last updated: 2016-08-31Bibliographically approved

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