Exercise i) Discuss when a) space-time-coding and b) the capacity-achieving precoding and combining solutions can be used. When can we only use approach a)? If we can use both a) and b), which is the best solution? ii) Suppose we have three users employing OFDM for downlink transmission to a base station. Describe how we optimally allocate powers to the users in order to maximize the total system capacity. iii) Talk about the latency in a cellular system: where time is spent in the various parts of the communication, from the user to the server where the end application is running? What are the technologies and solutions used in 5G networks to reduce latency? Which is the average latency in seconds) for 4G and 5G systems