Multi-receiver Aloha systems - a survey and new results
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paper_title: Mobile Radio Slotted ALOHA with Capture, Diversity and Retransmission Control in the Presence of Shadowing

paper_content:

In this paper, the capture performance of a random access scheme in the presence of Rayleigh fading, shadowing and diversity is studied. The conditional throughput C_n, i.e., the average number of packets which are correctly received per slot, given the number of colliding packets, n, is computed, as well as its limit as n\to\infty. Some different diversity schemes are compared. Also, retransmission control is considered as a means to enhance the system performance. The stability of the controlled system is directly proved. Finally, the effect of long-term attenuations on the system performance and stability is discussed.
---
paper_title: Diversity ALOHA--A Random Access Scheme for Satellite Communications

paper_content:

A generalization of the slotted ALOHA random access scheme is considered in which a user transmits multiple copies of the same packet. The multiple copies can be either transmitted simultaneously on different frequency channels (frequency diversity) or they may be transmitted on a single high-speed channel but spaced apart by random time intervals (time diversity). In frequency diversity, two schemes employing channel selections with and without replacements have been considered. In time diversity, two schemes employing a fixed number of copies or a random number of copies for each packet have been considered. In frequency diversity, activity factor-throughput tradeoffs and in time diversity, delay-throughput tradeoffs for various diversity orders have been compared. It is found that under light traffic, multiple transmission gives better delay performance. If the probability that a packet fails a certain number or more times is specified not to exceed some time limit (realistic requirement for satellite systems having large round trip propagation delay), then usually multiple transmission gives higher throughput.
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paper_title: Contention Resolution Diversity Slotted ALOHA (CRDSA): An Enhanced Random Access Schemefor Satellite Access Packet Networks

paper_content:

In this paper a new multiple access scheme dubbed contention resolution diversity slotted ALOHA (CRDSA) is introduced and its performance and implementation are thoroughly analyzed. The scheme combines diversity transmission of data bursts with efficient interference cancellation techniques. It is shown that CRDSA largely outperforms the classical lotted ALOHA (SA) technique in terms of throughput under equal packet loss ratio conditions (e.g. 17-fold improvement at packet loss ratio = 2 middot 10-2). CRDSA allows to boost the performance of random access (RA) channels in the return link of interactive satellite networks, making RA very efficient and providing low latency for the transmission of small size sparse packets. Implementation-wise it is shown that the CRDSA technique can be easily integrated in systems equipped with digital burst demodulators.
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paper_title: Cooperative Slotted Aloha for Multi-Base Station Systems

paper_content:

We introduce a framework to study slotted Aloha with cooperative base stations. Assuming a geographic-proximity communication model, we propose several decoding algorithms with different degrees of base stations' cooperation (non-cooperative, spatial, temporal, and spatio-temporal). With spatial cooperation, neighboring base stations inform each other whenever they collect a user within their coverage overlap; temporal cooperation corresponds to (temporal) successive interference cancellation done locally at each station. We analyze the four decoding algorithms and establish several fundamental results. With all algorithms, the peak throughput (average number of decoded users per slot, across all base stations) increases linearly with the number of base stations. Further, temporal and spatio-temporal cooperations exhibit a threshold behavior with respect to the normalized load (number of users per station, per slot). There exists a positive load $G^{\star}$ , such that, below $G^{\star} $ , the decoding probability is asymptotically maximal possible, equal the probability that a user is heard by at least one base station; with non-cooperative decoding and spatial cooperation, we show that $G^{\star} $ is zero. Finally, with spatio-temporal cooperation, we optimize the degree distribution according to which users transmit their packet replicas; the optimum is in general very different from the corresponding optimal distribution of the single-base station system.
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paper_title: The throughput of slotted aloha with diversity

paper_content:

In this paper, a simple variation of classical Slotted Aloha is introduced and analyzed. The enhancement relies on adding multiple receivers that gather different observations of the packets transmitted by a user population in one slot. For each observation, the packets transmitted in one slot are assumed to be subject to independent on-off fading, so that each of them is either completely faded, and then does not bring any power or interference at the receiver, or it arrives unfaded, and then may or may not, collide with other unfaded transmissions. With this model, a novel type of diversity is introduced to the conventional SA scheme, leading to relevant throughput gains already for moderate number of receivers. The analytical framework that we introduce allows to derive closed-form expression of both throughput and packet loss rate an arbitrary number of receivers, providing interesting hints on the key trade-offs that characterize the system. We then focus on the problem of having receivers forward the full set of collected packets to a final gateway using the minimum possible amount of resources, i.e., avoiding delivery of duplicate packets, without allowing any exchange of information among them. We derive what is the minimum amount of resources needed and propose a scheme based on random linear network coding that achieves asymptotically this bound without the need for the receivers to coordinate among them.
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paper_title: Graph-Based Random Access for the Collision Channel without Feedback: Capacity Bound

paper_content:

A random access scheme for the collision channel without feedback is proposed. The scheme is based on erasure correcting codes for the recovery of packet segments that are lost in collisions, and on successive interference cancellation for resolving collisions. The proposed protocol achieves reliable communication in the asymptotic setting and attains capacities close to 1 [packets/slot]. A capacity bound as a function of the overall rate of the scheme is derived, and code distributions tightly approaching the bound developed.
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paper_title: Overload control for Machine-Type-Communications in LTE-Advanced system

paper_content:

As Machine-Type-Communications (MTC) continues to burgeon rapidly, a comprehensive study on overload control approach to manage the data and signaling traffic from massive MTC devices is required. In this work, we study the problem of RACH overload, survey several types of RAN-level contention resolution methods, and introduce the current development of CN (core network) overload mechanisms in 3GPP LTE. Additionally, we simulate and compare different methods and offer further observations on the solution design.
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paper_title: Theoretical Analysis of the Capture Probability in Wireless Systems with Multiple Packet Reception Capabilities

paper_content:

In this paper, we address the problem of computing the probability that r out of n interfering wireless signals are "captured," i.e., received with sufficiently large Signal to Interference plus Noise Ratio (SINR) to correctly decode the signals by a receiver with multi-packet reception (MPR) and Successive Interference Cancellation (SIC) capabilities. We start by considering the simpler case of a pure MPR system without SIC, for which we provide an expression for the distribution of the number of captured packets, whose computational complexity scales with n and r. This analysis makes it possible to investigate the system throughput as a function of the MPR capabilities of the receiver. We then generalize the analysis to SIC systems. In addition to the exact expressions for the capture probability and the normalized system throughput, we also derive approximate expressions that are much easier to compute and provide accurate results in some practical scenarios. Finally, we present selected results for some case studies with the purpose of illustrating the potential of the proposed mathematical framework and validating the approximate methods.
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paper_title: Stability properties of slotted Aloha with multipacket reception capability

paper_content:

The stability of the Aloha random-access algorithm in an infinite-user slotted channel with multipacket-reception capability is considered. This channel is a generalization of the usual collision channel, in that it allows the correct reception of one or more packets involved in a collision. The number of successfully received packets in each slot is modeled as a random variable which depends exclusively on the number of simultaneously attempted transmissions. This general model includes as special cases channels with capture, noise, and code-division multiplexing. It is shown by drift analysis that the channel backlog Markov chain is ergodic if the packet-arrival rate is less than the expected number of packets successfully received in a collision of n as n goes to infinity. The properties of the backlog in the nonergodicity region are examined. >
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paper_title: On the integration of random access and DAMA channels for the return link of satellite networks

paper_content:

Recent advances in Random Access (RA), improving throughput and loss rates, make the usage of such technique particularly interesting to complement Demand Assigned Multiple Access (DAMA) channels for the return link of satellite systems. In this paper, a novel approach for the integration of the two access strategies aimed at transmission delay optimization is presented. An algorithm for DAMA and RA delay estimation is presented, and its accuracy shown by simulations. Furthermore, the benefits of the proposed integration concept are demonstrated with significant gains in delay and throughput in moderate to high load operating regions.
---
paper_title: Overload control for Machine-Type-Communications in LTE-Advanced system

paper_content:

As Machine-Type-Communications (MTC) continues to burgeon rapidly, a comprehensive study on overload control approach to manage the data and signaling traffic from massive MTC devices is required. In this work, we study the problem of RACH overload, survey several types of RAN-level contention resolution methods, and introduce the current development of CN (core network) overload mechanisms in 3GPP LTE. Additionally, we simulate and compare different methods and offer further observations on the solution design.
---
paper_title: Stability properties of slotted Aloha with multipacket reception capability

paper_content:

The stability of the Aloha random-access algorithm in an infinite-user slotted channel with multipacket-reception capability is considered. This channel is a generalization of the usual collision channel, in that it allows the correct reception of one or more packets involved in a collision. The number of successfully received packets in each slot is modeled as a random variable which depends exclusively on the number of simultaneously attempted transmissions. This general model includes as special cases channels with capture, noise, and code-division multiplexing. It is shown by drift analysis that the channel backlog Markov chain is ergodic if the packet-arrival rate is less than the expected number of packets successfully received in a collision of n as n goes to infinity. The properties of the backlog in the nonergodicity region are examined. >
---
paper_title: On the integration of random access and DAMA channels for the return link of satellite networks

paper_content:

Recent advances in Random Access (RA), improving throughput and loss rates, make the usage of such technique particularly interesting to complement Demand Assigned Multiple Access (DAMA) channels for the return link of satellite systems. In this paper, a novel approach for the integration of the two access strategies aimed at transmission delay optimization is presented. An algorithm for DAMA and RA delay estimation is presented, and its accuracy shown by simulations. Furthermore, the benefits of the proposed integration concept are demonstrated with significant gains in delay and throughput in moderate to high load operating regions.
---
paper_title: Analysis of the Capture Probability in Wireless Systems with Multi-Packet Reception Capabilities and Successive Interference Cancellation

paper_content:

In this paper, we address the problem of computing the probability that $r$ out of $n$ interfering signals can be correctly received in a random access wireless system with capture and capable of performing up to $K$ successive interference cancellation (SIC) iterations. We provide an expression for the distribution of the number of captured packets that is scalable with $n$ and $r$. We also provide an approximate expression for the mean number of captured signals, which gives the system throughput as a function of $K$ and $n$. The approximation is much easier to compute than the exact mean and provides good results for reasonable values of $K$. Finally, we present some selected results for a case study with the purpose of illustrating the potentialities of the proposed mathematical framework and validate the approximate method to compute the system throughput.
---
paper_title: The throughput of slotted aloha with diversity

paper_content:

In this paper, a simple variation of classical Slotted Aloha is introduced and analyzed. The enhancement relies on adding multiple receivers that gather different observations of the packets transmitted by a user population in one slot. For each observation, the packets transmitted in one slot are assumed to be subject to independent on-off fading, so that each of them is either completely faded, and then does not bring any power or interference at the receiver, or it arrives unfaded, and then may or may not, collide with other unfaded transmissions. With this model, a novel type of diversity is introduced to the conventional SA scheme, leading to relevant throughput gains already for moderate number of receivers. The analytical framework that we introduce allows to derive closed-form expression of both throughput and packet loss rate an arbitrary number of receivers, providing interesting hints on the key trade-offs that characterize the system. We then focus on the problem of having receivers forward the full set of collected packets to a final gateway using the minimum possible amount of resources, i.e., avoiding delivery of duplicate packets, without allowing any exchange of information among them. We derive what is the minimum amount of resources needed and propose a scheme based on random linear network coding that achieves asymptotically this bound without the need for the receivers to coordinate among them.
---
paper_title: The on-off fading channel

paper_content:

We introduce a simple on-off fading dis- crete memoryless multiple-access channel in which the multiplicative fading for each user is a Bernoulli ran- dom process. We find the capacity of this channel in the case that the receiver does not know the values of the channel gains.
---
paper_title: Theoretical Analysis of the Capture Probability in Wireless Systems with Multiple Packet Reception Capabilities

paper_content:

In this paper, we address the problem of computing the probability that r out of n interfering wireless signals are "captured," i.e., received with sufficiently large Signal to Interference plus Noise Ratio (SINR) to correctly decode the signals by a receiver with multi-packet reception (MPR) and Successive Interference Cancellation (SIC) capabilities. We start by considering the simpler case of a pure MPR system without SIC, for which we provide an expression for the distribution of the number of captured packets, whose computational complexity scales with n and r. This analysis makes it possible to investigate the system throughput as a function of the MPR capabilities of the receiver. We then generalize the analysis to SIC systems. In addition to the exact expressions for the capture probability and the normalized system throughput, we also derive approximate expressions that are much easier to compute and provide accurate results in some practical scenarios. Finally, we present selected results for some case studies with the purpose of illustrating the potential of the proposed mathematical framework and validating the approximate methods.
---
paper_title: On the integration of random access and DAMA channels for the return link of satellite networks

paper_content:

Recent advances in Random Access (RA), improving throughput and loss rates, make the usage of such technique particularly interesting to complement Demand Assigned Multiple Access (DAMA) channels for the return link of satellite systems. In this paper, a novel approach for the integration of the two access strategies aimed at transmission delay optimization is presented. An algorithm for DAMA and RA delay estimation is presented, and its accuracy shown by simulations. Furthermore, the benefits of the proposed integration concept are demonstrated with significant gains in delay and throughput in moderate to high load operating regions.
---
paper_title: Mobile Radio Slotted ALOHA with Capture, Diversity and Retransmission Control in the Presence of Shadowing

paper_content:

In this paper, the capture performance of a random access scheme in the presence of Rayleigh fading, shadowing and diversity is studied. The conditional throughput C_n, i.e., the average number of packets which are correctly received per slot, given the number of colliding packets, n, is computed, as well as its limit as n\to\infty. Some different diversity schemes are compared. Also, retransmission control is considered as a means to enhance the system performance. The stability of the controlled system is directly proved. Finally, the effect of long-term attenuations on the system performance and stability is discussed.
---
paper_title: Diversity ALOHA--A Random Access Scheme for Satellite Communications

paper_content:

A generalization of the slotted ALOHA random access scheme is considered in which a user transmits multiple copies of the same packet. The multiple copies can be either transmitted simultaneously on different frequency channels (frequency diversity) or they may be transmitted on a single high-speed channel but spaced apart by random time intervals (time diversity). In frequency diversity, two schemes employing channel selections with and without replacements have been considered. In time diversity, two schemes employing a fixed number of copies or a random number of copies for each packet have been considered. In frequency diversity, activity factor-throughput tradeoffs and in time diversity, delay-throughput tradeoffs for various diversity orders have been compared. It is found that under light traffic, multiple transmission gives better delay performance. If the probability that a packet fails a certain number or more times is specified not to exceed some time limit (realistic requirement for satellite systems having large round trip propagation delay), then usually multiple transmission gives higher throughput.
---
paper_title: The throughput of slotted aloha with diversity

paper_content:

In this paper, a simple variation of classical Slotted Aloha is introduced and analyzed. The enhancement relies on adding multiple receivers that gather different observations of the packets transmitted by a user population in one slot. For each observation, the packets transmitted in one slot are assumed to be subject to independent on-off fading, so that each of them is either completely faded, and then does not bring any power or interference at the receiver, or it arrives unfaded, and then may or may not, collide with other unfaded transmissions. With this model, a novel type of diversity is introduced to the conventional SA scheme, leading to relevant throughput gains already for moderate number of receivers. The analytical framework that we introduce allows to derive closed-form expression of both throughput and packet loss rate an arbitrary number of receivers, providing interesting hints on the key trade-offs that characterize the system. We then focus on the problem of having receivers forward the full set of collected packets to a final gateway using the minimum possible amount of resources, i.e., avoiding delivery of duplicate packets, without allowing any exchange of information among them. We derive what is the minimum amount of resources needed and propose a scheme based on random linear network coding that achieves asymptotically this bound without the need for the receivers to coordinate among them.
---
paper_title: Theoretical Analysis of the Capture Probability in Wireless Systems with Multiple Packet Reception Capabilities

paper_content:

In this paper, we address the problem of computing the probability that r out of n interfering wireless signals are "captured," i.e., received with sufficiently large Signal to Interference plus Noise Ratio (SINR) to correctly decode the signals by a receiver with multi-packet reception (MPR) and Successive Interference Cancellation (SIC) capabilities. We start by considering the simpler case of a pure MPR system without SIC, for which we provide an expression for the distribution of the number of captured packets, whose computational complexity scales with n and r. This analysis makes it possible to investigate the system throughput as a function of the MPR capabilities of the receiver. We then generalize the analysis to SIC systems. In addition to the exact expressions for the capture probability and the normalized system throughput, we also derive approximate expressions that are much easier to compute and provide accurate results in some practical scenarios. Finally, we present selected results for some case studies with the purpose of illustrating the potential of the proposed mathematical framework and validating the approximate methods.
---
paper_title: The throughput of slotted aloha with diversity

paper_content:

In this paper, a simple variation of classical Slotted Aloha is introduced and analyzed. The enhancement relies on adding multiple receivers that gather different observations of the packets transmitted by a user population in one slot. For each observation, the packets transmitted in one slot are assumed to be subject to independent on-off fading, so that each of them is either completely faded, and then does not bring any power or interference at the receiver, or it arrives unfaded, and then may or may not, collide with other unfaded transmissions. With this model, a novel type of diversity is introduced to the conventional SA scheme, leading to relevant throughput gains already for moderate number of receivers. The analytical framework that we introduce allows to derive closed-form expression of both throughput and packet loss rate an arbitrary number of receivers, providing interesting hints on the key trade-offs that characterize the system. We then focus on the problem of having receivers forward the full set of collected packets to a final gateway using the minimum possible amount of resources, i.e., avoiding delivery of duplicate packets, without allowing any exchange of information among them. We derive what is the minimum amount of resources needed and propose a scheme based on random linear network coding that achieves asymptotically this bound without the need for the receivers to coordinate among them.
---

Title: Multi-receiver Aloha Systems - A Survey and New Results

Section 1: INTRODUCTION
Description 1: Provide an overview of random access schemes with a focus on the challenges and opportunities in multi-receiver Aloha systems, capturing aspects like collision handling, capture effect, and multi-packet reception.

Section 2: PRELIMINARIES AND SYSTEM MODELS
Description 2: Detail the system model used, including assumptions about the user and receiver distribution, channel models, packet transmission, and reception mechanisms.

Section 3: On-Off Fading Channel (OOF)
Description 3: Describe the OOF channel model, explaining the assumptions and implications of modeling wireless links as packet erasure channels with independent and identically distributed properties.

Section 4: Perfect Power Control (PPC)
Description 4: Discuss the PPC channel model, focusing on the role of Rayleigh fading, power control, and signal-to-interference ratio in packet decoding under these conditions.

Section 5: Equal Transmission Power (ETP)
Description 5: Introduce the ETP scenario, where the effects of user-receiver distance are considered, and how it impacts signal power and system performance when power control is not performed.

Section 6: AN ANALYTICAL COMPARISON UNDER ON-OFF FADING AND PERFECT POWER CONTROL MODELS
Description 6: Present an analytical framework to compare system performance under the OOF and PPC models, including mathematical formulations and throughput evaluations.

Section 7: NUMERICAL RESULTS
Description 7: Discuss numerical simulations and their results, focusing on the impact of non-i.i.d. incoming powers, spatial distribution of users, and multiple packet reception capabilities on system performance.

Section 8: CONCLUSIONS
Description 8: Summarize the key findings of the study, emphasizing the theoretical and practical implications, and suggest directions for future research on multi-receiver Aloha systems.