Add tutorial about how to run multiple UEs

* multiple UEs with namespaces (provided new script)
* multiple UEs with Docker UEs
* updated rfsimulator and channel simulation tutorials
* updated README.md

Co-authored-by: Arash Sahbafard <arash.sahbafard@silicon-austria.com>

tools/scripts/multi-ue.sh

@@ -0,0 +1,67 @@
+#!/bin/bash
+
+ue_id=-1
+
+create_namespace() {
+  ue_id=$1
+  local name="ue$ue_id"
+  echo "creating namespace for UE ID ${ue_id} name ${name}"
+  ip netns add $name
+  ip link add v-eth$ue_id type veth peer name v-ue$ue_id
+  ip link set v-ue$ue_id netns $name
+  BASE_IP=$((200+ue_id))
+  ip addr add 10.$BASE_IP.1.100/24 dev v-eth$ue_id
+  ip link set v-eth$ue_id up
+  iptables -t nat -A POSTROUTING -s 10.$BASE_IP.1.0/255.255.255.0 -o lo -j MASQUERADE
+  iptables -A FORWARD -i lo -o v-eth$ue_id -j ACCEPT
+  iptables -A FORWARD -o lo -i v-eth$ue_id -j ACCEPT
+  ip netns exec $name ip link set dev lo up
+  ip netns exec $name ip addr add 10.$BASE_IP.1.$ue_id/24 dev v-ue$ue_id
+  ip netns exec $name ip link set v-ue$ue_id up
+}
+
+delete_namespace() {
+  local ue_id=$1
+  local name="ue$ue_id"
+  echo "deleting namespace for UE ID ${ue_id} name ${name}"
+  ip link delete v-eth$ue_id
+  ip netns delete $name
+}
+
+list_namespaces() {
+  ip netns list
+}
+
+open_namespace() {
+  if [[ $ue_id -lt 1 ]]; then echo "error: no last UE processed"; exit 1; fi
+  local name="ue$ue_id"
+  echo "opening shell in namespace ${name}"
+  echo "type 'ip netns exec $name bash' in additional terminals"
+  ip netns exec $name bash
+}
+
+usage () {
+  echo "$1 -c <num>: create namespace \"ue<num>\""
+  echo "$1 -d <num>: delete namespace \"ue<num>\""
+  echo "$1 -e      : execute shell in last processed namespace"
+  echo "$1 -l      : list namespaces"
+  echo "$1 -o <num>: open shell in namespace \"ue<num>\""
+}
+
+prog_name=$(basename $0)
+
+if [[ $(id -u) -ne 0 ]] ; then echo "Please run as root"; exit 1; fi
+if [[ $# -eq 0 ]]; then echo "error: no parameters given"; usage $prog_name; exit 1; fi
+
+while getopts c:d:ehlo: cmd
+do
+  case "${cmd}" in
+    c) create_namespace ${OPTARG};;
+    d) delete_namespace ${OPTARG};;
+    e) open_namespace; exit;;
+    h) usage ${prog_name}; exit;;
+    l) list_namespaces;;
+    o) ue_id=${OPTARG}; open_namespace;;
+    /?) echo "Invalid option"; usage ${prog_name}; exit;;
+  esac
+done