This paper considers transmission of scheduling information in  OFDMA-based cellular communication systems such as 3GPP long-term  evolution (LTE). These systems provide efficient usage of radio  resources by allowing users to be scheduled dynamically in both  frequency and time. This requires considerable amounts of scheduling  information to be sent to the users.  The paper compares two basic transmission strategies: transmitting a  separate scheduling message to each user versus broadcasting a joint  scheduling message to all users. Different scheduling granularities  are considered, as well as different scheduling algorithms. The  schemes are evaluated in the context of the LTE downlink using  multiuser system simulations, assuming a full-buffer situation.  The results show that separate transmission of the scheduling  information requires a slightly lower overhead than joint  broadcasting, when proportional fair scheduling is employed and the  users are spread out over the cell area. The results also indicate  that the scheduling granularity standardized for LTE provides a good  trade-off between scheduling granularity and overhead.

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.

This paper considers the control signaling on the downlink in wireless multiple access systems, with focus on the part of the control signaling that carries information on the user's time/frequency scheduling assignments. A new idea is presented to reduce the amount of channel resources needed for this signaling. The idea is to exploit the fact that provided that only one single user is scheduled on each channel resource, then the different users' scheduling assignments are correlated. This correlation can be exploited by encoding the scheduling information differentially. In order to recover the scheduling information, a user must then decode the scheduling information of some of the others. This is possible, because on the downlink, all users can hear the transmission by the base station so that users with a high SNR may decode the control signaling sent to users with a lower SNR. We present a practical scheme to exploit this idea. Both analytical analysis and numerical examples illustrate that the proposed technique can provide a substantial reduction in signaling traffic.

We provide an analytical framework for optimizing the resources required for signaling of control information in wireless multiple access systems. In doing so, we use recent results in information theory, namely a new bound on the achievable rate in the finite blocklength regime by Polyanskiy. We formulate optimization problems for finding the minimum required number of channel uses such that the overall error probability in decoding the control information is below a given threshold for three different control signaling schemes.

We present a fast algorithm that, for a given input sequence and a linear channel code, computes the syndrome posterior probability (SPP) of the code, i.e., the probability that all parity check relations of the code are satisfied. According to this algorithm, the SPP can be computed blindly, i.e., given the soft information on a received sequence we can compute the SPP for the code without first decoding the bits. We show that the proposed scheme is efficient by investigating its computational complexity.

We then consider two scenarios where our proposed SPP algorithm can be used. The first scenario is when we are interested in finding out whether a certain code was used to encode a data stream. We formulate a statistical hypothesis test and we investigate its performance. We also compare the performance of our scheme with that of an existing scheme. The second scenario deals with how we can use the algorithm for reducing the computational complexity of blind decoding process, the process that, for instance, is used by terminals in LTE for detection of control information. We propose a heuristic sequential statistical hypotheses test to use the fact that in real applications, the data arrives sequentially, and we investigate its performance using system simulations.

Blind decoding of control information is used in some wireless  multiple access systems such as LTE to achieve adaptive modulation  and coding, as well as to address the multiple access problem on the  control channel. Blind decoding incurs high computational complexity in mobile terminals. In this paper, we describe a scheme to reduce  the computational complexity associated with the blind decoding. The  main idea is to broadcast a "please-decode-blindly" message to all  terminals that are eligible for scheduling, to instruct a subset of  the terminals to perform the blind search. We propose two schemes to  implement our idea and we investigate their performances via system  simulations.

Blind decoding, used on control channels of some multi-user wireless  access systems, is a technique for achieving adaptive modulation and  coding. The idea is to adapt the modulation and coding scheme to the  channel quality but instead of signaling the parameters used  explicitly, the receiver blindly tries a number of fixed parameter  combinations until a successful decoding attempt is detected, with  the help of a cyclic redundancy check. In this paper we suggest a  new method for reducing the complexity and energy consumption  associated with such blind decoding schemes. Our idea is to use a  mini-CRC injected early in the data stream to determine if the  current decoding attempt is using the correct modulation and coding  parameters. We analyze and exemplify the complexity gain of this  approach and also investigate the impact of the rearrangement of the  CRC scheme in terms of the probability of undetected error. The  presented results for the complexity gain are promising and the  impact on the error detection capability turns out to be small if  any.