The Chargers added experienced depth to their defensive line on Monday when they acquired defensive lineman Travis Johnson from the Texans in exchange for an undisclosed 2010 draft choice. San Diego also signed LSU wide receiver Demetrius Byrd, the team's seventh-round choice this year, to a four-year contract. He continues to make progress in his recovery from an automobile accident suffered prior to the draft. In addition, the team waived wide receiver Greg Carr, tackle Dan Gay and wide receiver Rodgeriqus Smith. All three players joined the Chargers as undrafted free agents in May.