# Slotted ALOHA :::success - [x] Step 1: Background knowledge (with text and figures) * [x] Step 2: System model (I/P parameters, system architecture and timing diagram) * [x]Step 3a: Specify the constant * [ ]Step 3b: Draw a timing diagram showing the transmission behavior of a STA * [x] Step 4: Simulator (Data structure, flowchart) * [ ]Step 5: Verification of values generated from the simulator and Step 3b * [x]Step 6: Simulation results ::: ## Step 1: Background Knowledge :::info Summarize the background knowledge (with text and figures) ::: - **In slotted ALOHA**, time is assumed to be slotted in timeslots of duration $τ$, and STAs can only start their packet transmissions at the beginning of the next timeslot after the packet has formed ![](https://i.imgur.com/NJDP2NF.jpg) - Each STAs can have two states: ***idle*** or ***backlogged***. - When a STA has nothing to transmit it is in the idle state. - If the packet was received successfully the STA enters the idle state again, *otherwise* it goes to backlogged state. :::success ***Idle State*** - As there are a total of $m$ STAs in the network, each of the $m−n$ nonbacklogged STAs will transmit a packet **immediately** in the given slot if one or more packets arrived at these STAs - These new arrivals are Poisson distributed with mean $λ$, so probability of no arrivals is $e^{-λ/m}$ - This implies that the probability of an unbacklogged STA transmits packets in a given slot is $P_a = 1-e^{-λ/m}$ ::: :::success ***Backlogged state*** - Each backlogged STAs retransmits with probability $P_r$ in each successive slot until successful transmission happens - Let $n$ denote the number of backlogged STAs at the beginning of a given slot, each of the STAs will transmit a packet in a given slot independent of the other nodes, with probability $P_r$ ::: - $G=λτ$ is offered load, and throughput $S=Ge^{-G}$ - Collision Probability $P_c=1-Ge^{-G}-e^{-G}$ - Mean delay $\overline{D_{}}=1-{1/λ}+{m/S}$ ## Step 2: System Model :::info Define the problem by specifying the system model you considered ::: - There are m STAs, - Time is divided into fixed-length slots - Packet arrivals are poisson distribution with mean $λ$ - When STAs are in the idle state, probability of new arrival for each STAs is $P_a = 1-e^{-λ/m}$ - When in backlogged state, probability of retransmission is $P_r=P_a = 1-e^{-λ/m}$ - An STA will stay in backlogged state until the packet is successful, when the packet is successful STA will become idle and waiting for a new packet arrival ![](https://i.imgur.com/liwjq8s.jpg) *Figure 2.1 Timing Diagram* ## Step 3: Draw figures to show the concepts you learned ### 3a. Specify the constants you used in the figures :::info specify I/P parameters ::: | I/P | Value | | -------- | -------- | | number of STAs | 100 | | $λ$ | [0:0.1:5] | | simulation Time | $10^5$ timeslots | ### 3b. Draw a timing diagram showing the transmission behavior of a STA :::info Draw a timing dirgram showing the concepts you learned ::: ## Step 4 : Simulator :::info Write a simulator to verify the concept ::: ### 4a. Define the parameters (their ranges need to be specified) and data structures to be used in your simulator #### STA's Data structure | datatype | meaning | range | | -------- | -------- | -------- | | int[status]| STA status, idle or backlogged | $[0,1]$ | | float[pa] | packet arrival probability | $[0,1]$ | | float[pr] | packet retransmission probability | $[0,1]$ | |int[N] | packet transmitted in a given slot|$[0,100]$ | | int[totalPacketAt] |total packets attempted| | | int[totalPacketTr] |total packets successfully transmitted| | |O/P| |-|-| |$p$ : packet collision probability | |$S$ : throughput | |$G$ : offered load | |$\overline{D_{}}$ : mean delay | ### 4b. Draw the flowchart ![](https://i.imgur.com/zttUK4e.jpg) ## Step 5 : Verification :::info Implement a simulator. Use the values you generated from the simulator and verified them one-by-one based on Step 3 ::: >this is the transmission behavior when lambda=1 https://raw.githubusercontent.com/bariqfirmansyah/slottedaloha/master/lambda1.txt this is also the transmission behavior when lambda=1 https://raw.githubusercontent.com/bariqfirmansyah/slottedaloha/master/lambda1a.txt this is the transmission behavior when lambda=5 https://raw.githubusercontent.com/bariqfirmansyah/slottedaloha/master/lambda5.txt >look at how the packet transmission occurs more when lambda=5 ## Step 6 : Simulation Result :::info Show us the simulation results ::: ![](https://i.imgur.com/wjZ7fCZ.jpg) ![](https://i.imgur.com/wLf87aX.jpg) ![](https://i.imgur.com/YoBk17h.jpg)
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<center> Pre-Intern Notes </center>

Topic: Random Access Procedure for 802.11ax Bariq S. Firmansyah Institut Teknologi Bandung email [5G] Research on Random Access: A. 3GPP LTE/5G NR; B. IEEE 802.11ax (Supervisor Ray: I~III should be done before April) Goal: (A) Performance evaluation of the random access channel for 4G/5G networks (B) Performance evaluation of the Uplink OFDMA Random Access (UORA) in 802.11ax Slotted ALOHA

9/10/2020
#Slotted ALOHA

Topic: 5G Random Access Procedure Bariq Sufi Firmansyah Institut Teknologi Bandung bariqsufif@gmail.com Background ::: spoiler Click to view the background knowledge of Pure ALOHA, you can skip this if you already understand The network is constructed such that each station is coupled to a single passive channel, for example a coaxial cable In normal operation packets are transmitted without error from one station to another and each packet is acknowledged If two stations try to transmit at the same time, then the signals interfere and an error is detected by the receiving station and no acknowledgement is sent

7/17/2020
2020/7/1 Report

Why do I do this job? Because I want to analyze the performance of UORA in 802.11 ax What do I want to do? Continue writing the timing diagram, flow chart and performance evaluation Sum of the job I analyze the simulation result and compare it to the analytical model Expected Outcome Finish writing the timing diagram, flow chart and performance evaluation Intro UL OFDMA is the multi-user variant of the OFDM whereby assigning subsets of subcarriers, called resource unit (RU), to different users allows simultaneous transmissions of data, control, and management frames from several users so it can serve more users at the same time The MU UL transmissions are solicited by the AP in a new control frame called trigger frame (TF). A STA that is the intended receiver of the TF responds with an HE trigger-based PPDU UL OFDMA RA is a mechanism that enables a STA to transmit an UL physical layer protocol data unit (PPDU) in an RU access under UL OFDMA even if it has not been explicitly addressed. A STA uses a random back-off procedure before it randomly selects any one of the multiple RUs assigned for random access for its UL transmission

7/1/2020
#One-Shot Random Access

Topic: 5G Random Access Procedure Bariq Sufi Firmansyah Institut Teknologi Bandung bariqsufif@gmail.com Background One-Shot Random Access: Analytical Model In this system, time is divided into fix-length ‘access cycle.’ Each access cycle contains $N$ RAOs. All of the $M$ devices transmit their first random-access attempts at a randomly chosen RAO in the first access cycle. The collided devices immediately re-transmit their random-access attempts in the next access cycle. A total of $I_{max}$ access cycles are reserved.

7/1/2020
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