Intra-Body　Communication　(IBC),　which　employs　the　human　body　as　the　channel　to　transmit　health　informatics,　is　a　potential　approach　for　connecting　wearable　and　implantable　devices.　Undoubtedly,　its　channel　characteristics　provide　deep　insights　to　select　parameters　that　are　beneficial　for　the　physical　layer　design　of　the　Body　Area　Network　(BAN).　Nevertheless,　such　analysis　has　not　been　systematically　addressed.　To　this　end,　the　transfer　function　from　the　quasi-static　model　in　the　electromagnetic　field　is　considered　at　first.　Then,　the　linearity　of　the　galvanic　coupling　IBC　channel　is　verified.　Besides,　the　proper　frequency　band　for　data　transmission　is　investigated　using　the　water-filling　algorithm.　Moreover,　the　theoretical　Bit　Error　Rate　(BER)　performances　of　different　modulations　are　studied.　Results　revealed　that　the　galvanic　coupling　IBC　channel　can　be　modeled　as　a　linear　band-limited　Additive　White　Gaussian　Noise　(AWGN)　channel.　Finally,　suitable　modulations　for　various　scenarios　are　discussed　based　on　the　channel　characteristics　found.　Consequently,　this　work　can　further　enrich　the　design　of　the　IBC　for　medical　applications.　©　2016　IEEE.