It will surprise many that for deep Space communications only 50Mhz can be used at X-Band, our most utilized Band. Split into 37 channels with 1.358Mhz spacing, normally "space" is good separator when it comes to inter channel interference...
But what happens when you have a number of spacecraft in the same antenna beam? Mars is becoming problematic when it comes to communications. The "space" separation goes out the window and suddenly you have 11 (current) spacecraft sharing a 50Mhz chunk of spectrum...
For the low telemetry rate spacecraft or landers a single channel is enough. But for Mars Reconnaissance Orbiter that can pump down 6Mbps it need lots of room. It needs a minimum of 4 channels either side of its allocated one to accommodate telemetry ..
We do have Ka band which has a larger allocated spectrum but this can be heavily impacted by weather. When humans start making the journey with live video feeds and huge telemetry rates it makes you wonder, how are we going to do it? I have no idea