Interpolation and decimation implementation

I am trying to implement interpolation and decimation without using build in functions for this purpose i follow the following sequence

upsampling->filter (interpolation)

filter->downsample (Decimation)

for interpolation filter i use fir interpolation and for decimation i use window hamming method but the problem is whenever i handle the group delay my symobls are reduced. So what should i do to handle this problem.

My code is written below

clc;

clear all;

close all;

idata=ones(1,100);

nfilt=30;

upfac = 10;

alpha = 0.5;

xr = upsample(idata,upfac);

h1 = intfilt(upfac,2,alpha);

y = filter(h1,1,xr);

delay = mean(grpdelay(h1));

y(1:delay) = [];

[B,A]=fir1(30,1/10);

nfilt = nfilt+1;

itemp = 2*idata(1) - idata((nfilt+1):-1:2);

[itemp,zi]=filter(B,1,itemp); %#ok

dec_filter=filter(B,A,y,zi);

delay = mean(grpdelay(B));

dec_filter(1:delay) = [];

dec=downsample(dec_filter,10);

xx=decimate(y,10,'fir');